Level of physical activity and other maternal characteristics during the third trimester of pregnancy and its association with birthweight at term in South Ethiopia: A prospective cohort study

Meseret Legesse; Jemal Haider Ali; Md Dilshad Manzar; Mohammed Salahuddin; Hamid Yimam Hassen

doi:10.1371/journal.pone.0236136

. 2020 Jul 20;15(7):e0236136. doi: 10.1371/journal.pone.0236136

Level of physical activity and other maternal characteristics during the third trimester of pregnancy and its association with birthweight at term in South Ethiopia: A prospective cohort study

Meseret Legesse ^1,^#, Jemal Haider Ali ^1,^#, Md Dilshad Manzar ², Mohammed Salahuddin ³, Hamid Yimam Hassen ^4,^5,^*,^#

Editor: Frank T Spradley⁶

PMCID: PMC7371203 PMID: 32687541

Abstract

Birthweight continues to be the leading infant health indicator and the main focus of infant health policy. Low birthweight babies are at a higher risk of mortality and morbidity in most low-income countries. However, the physical activity level of pregnant women and its association with low birthweight is not well studied in Ethiopia. To address the above gap, we aimed to examine the maternal physical activity level and other characteristics during the third trimester and its association with birthweight at term in South Ethiopia. A community-based prospective cohort study was conducted among 247 randomly selected women in their third trimester of pregnancy. We measured the physical activity level using the Global Physical Activity Questionnaire, which included the type and level of various categories of activities. Anthropometric measurements of mothers were taken following standard procedures, and birthweight was recorded within 72 hours of delivery. To identify the effect of physical activity level and other maternal characteristics on low birthweight, we performed a multivariable logistic regression analysis. Overall, 111 (47.2%) mothers were engaged in vigorous physical activities during third trimester. The incidence of low birthweight was 21.6% and 9.68% among newborns of mothers who engaged in vigorous and moderate or low physical activity, respectively. The incidence of low birthweight at term was significantly associated with vigorous physical activity [adjusted odds ratio (AOR) = 2.48; 95% confidence interval (CI): 1.01–6.09], prolonged standing [AOR = 3.37; 95% CI: 1.14–9.93], and squatting [AOR = 2.61; 95% CI: 1.04–6.54)] during the third trimester of pregnancy. The vast majority of pregnant women were engaged in vigorous physical activities in their third trimester. Engagement in vigorous physical activity, standing for longer hours, and squatting were the major contributors to low birthweight at term. Hence, focused counseling should be conducted to reduce vigorous physical activity, standing, and squatting during the third trimester among pregnant women.

Introduction

Low birthweight (LBW) continued to be a significant public health problem, globally, with the highest prevalence in low- and middle-income countries (LMICs). The United Nations Children‘s Fund reported a global LBW rate of 14.6%, and more than 91% of LBW infants are born in LMICs [1]. It is an important public health concern, which influences the child’s health and nutritional status, physical growth, psychosocial development, and survival [2]. It is among the leading predictors of infant mortality within the first month of life [3]. Later in life, LBW is associated with chronic diseases such as high blood pressure, diabetes, coronary heart disease, and renal insufficiency [4–6]. The prevalence of LBW varies across countries and regions, with higher burden in sub-Saharan Africa and Southeast Asia [7, 8]. In Ethiopia, the prevalence of LBW varies across geographical areas, which ranges from 10% to 28% [9–12]. According to the 2016 Ethiopian Demographic and Health Survey (EDHS), 13% of babies in Ethiopia had LBW [13]. In the same breath, a recent meta-analysis in the country also documented a pooled LBW prevalence of 17.3% [14].

The primary causes for LBW are premature birth and intrauterine growth restriction or a combination of both, in addition to maternal attributes, indicating multifactorial etiologies. Socioeconomic factors such as unfavorable socioeconomic conditions, place of residence, age at pregnancy, maternal level of education, and occupation are risk factors for LBW [9, 10, 15–17]. Physical and behavioral characteristics, including low maternal weight at conception, short maternal stature, maternal comorbidities, absence or inadequate prenatal care, unfavorable reproductive history, absence of antenatal care, birth order and interval, multiple pregnancy, and illicit drug use considerably increase the likelihood of LBW [12, 17–20].

Women from poor communities often engage in heavy physical activities at home and in farms, and they usually have unfavorable birth outcomes, such as LBW, among others [21]. According to a Kenyan study, a majority of women spent 78% of their day-time on engaging in physical activities even during pregnancy [22], and presumably, a similar level of activities also prevails in Ethiopia, which has one of the highest prevalence of LBW.

To reduce the prevalence of LBW, Ethiopia has been implementing various intervention strategies under its National Nutrition Program (NNP), and has signed the Scaling Up Nutrition target to reduce undernutrition, focusing on the first 1,000 days [23]. The level of physical activity during pregnancy and its association with birthweight is widely documented in high-income countries; consequently, these countries developed guidelines on the recommended level of physical activity for pregnant women in each trimester of pregnancy. Nonetheless, such studies in Ethiopia are scant; thus, we aimed to examine the type and level of maternal physical activities and other characteristics during the third trimester and their association with birthweight at term to avail evidences for some programmatic initiatives.

Methods and materials

Study setting

The study was conducted at the Butajira Health and Demographic Surveillance Site (HDSS) in Butajira woreda, Southern Nations, Nationalities, and Peoples’ Region (SNNPR) of Ethiopia. Butajira woreda is located 130 km away from Addis Ababa, the capital city of Ethiopia. The Butajira HDSS was established in 1986 and covers nine rural and one urban kebeles (lowest administrative unit in Ethiopia) and has an estimated total population of 76,350. This study was conducted from January to June 2017.

Study design and study participants

We conducted a prospective cohort study among pregnant women in the Butajira HDSS. Pregnant women who were in their third trimester (31 to 34 weeks of gestation) during the study period were enrolled, while those who had diabetes mellitus, hypertension, and previous preterm baby were excluded to avoid confounding effect. After obtaining the data on sociodemographic characteristics, obstetric history, and physical activity level at baseline, mothers who performed vigorous physical activities were considered as the exposed group, and those who performed moderate or low intensity physical activities were considered as the non-exposed group.

Sample size and sampling procedure

We calculated the sample size using Epi-info version 7 StatCalc sample size calculation package for cohort studies, assuming an estimated LBW prevalence of 9.8% among women in the unexposed group, as reported in SNNPR [13]; a 15% difference between the exposed and unexposed group; an 80% power; and a 95% level of confidence. Adding 10% non-response, the final sample size was determined to be 247 women.

All 10 kebeles in the Butajira HDSS site were selected purposively, considering the better follow-up experience of the population. In order to recruit the participants, we prepared a sampling frame. It constituted a list of names of pregnant women who were thought to be in their third trimester and their detailed information, which included their house number and names of kebeles from the HDSS pregnancy survey list. Using the list, the mothers were visited at home, and based on their last menstrual period (LMP), women in their third trimester, particularly 31 to 34 weeks were identified. The sample size was distributed proportionally based on the number of third trimester mothers living in each kebele. Then, the participants were selected from each cluster using simple random sampling.

Data collection procedure

Data were collected through face-to-face interview, using a structured and pretested questionnaire, which was adapted from the EDHS and other peer reviewed articles. The height of the mother was measured to the nearest 0.1 cm using a wooden stadiometer with a sliding head bar and the mother on barefoot. Mid-upper arm circumference (MUAC) was also measured to the nearest 0.1 cm on the left arm, using an adult MUAC tape, following standard procedure. Pre-pregnancy weight was self-reported, and current weight was measured using a digital weighing scale. The difference between pre-pregnancy weight and current weight was used for estimating the weight gain during pregnancy. The main outcome, weight of the newborn, was measured by trained data collectors within 72 hours after birth using a digital weighing scale. To assess the level of physical activity, we employed the modified global physical activity questionnaire, standardized for low-income countries [24]. The questionnaire measured the level of physical activity of the women within the last 7 days prior to enrollment and contains a list of activities with different domains, frequencies of each activity per week, and durations per day. The type of physical activity at work, travel, and sports or leisure time activities were assessed. The level was then classified as vigorous activities, moderate activities, walking, and sitting/reclining. Then, we dichotomized women into those who performed vigorous physical activities and those who do not (including moderate and low physical activity level). Positions like standing for longer hours, squatting during routine daily physical activity, and lifting heavy loads were also assessed. We assessed the dietary habit of the mother during pregnancy using a food frequency questionnaire (FFQ). The FFQ was prepared to measure the estimated frequency of consumption for a specific food type within one month prior to the baseline survey.

Data quality control measures

We conducted a 2-day training on interview techniques, physical activity, and anthropometric measurements. The questionnaire was translated into the local language and reviewed for consistency. We also conducted a pilot test in an adjacent zone called ‘Silte’, which has similar socioeconomic, cultural, and geographical characteristics as those of the study area. We performed an internal consistency test using the pilot data, and results showed acceptable level (Cronbach’s alpha = 0.79). The collected data were assessed by field supervisors on a daily basis for incompleteness and/or inconsistencies. The anthropometric and birthweight measurement scales were calibrated frequently.

Definition of terms

Standing for a long period was defined as standing for more than 3 hours per day on average. Vigorous activities were described as activities that require a large amount of physical effort and largely increase breathing or heart rate (e.g., carrying or lifting heavy loads, digging, and construction work). Meanwhile, moderate activities were described as activities that require moderate physical effort and mildly increase breathing or heart rate (e.g., brisk walking and carrying light loads). Sedentary behavior was defined as sitting or reclining at work or at home; while getting to and from places; travelling in a car, bus, motor, or cart; reading; or watching television.

Statistical methods

The data, upon checks for completeness and consistency, were entered and cleaned using EpiData version 3.1., and then exported to STATA version 14.0 for further processing and analysis. Of the 247 participants enrolled in this study, 11 (4.5%) did not have information on birthweight and 1 (0.4%) born preterm and thus were removed from the analysis. Descriptive statistics including frequencies with percentage or means and standard deviations (SD) were computed as needed. To determine the wealth index, a principal component analysis of housing infrastructure and ownership of household assets was performed, and the score was consequently divided into five quintiles (lowest, second, middle, fourth, and highest). Depending on their engagement in daily physical activity, mothers were categorized into the vigorous intensity physical activity group and moderate or low intensity physical activity group. A bivariable analysis was carried out to determine the crude association of predictor variables with low birthweight, and based on the results, variables significant at p-value <0.05 were selected for multivariable analysis. To identify the major determinants of LBW, a multivariable logistic regression was performed. The variable antenatal care (ANC) follow up was excluded from the multivariable model due to collinearity with iron folic acid supplementation. The adjusted odds ratio (AOR) with its 95% confidence interval (CI) was used to determine the strength and significance of the association. A p-value of <0.05 was considered statistically significant.

Participant consent and ethical approval

The protocol of this study was approved by the institutional review board of the College of Health Sciences, Addis Ababa University. Written informed consent and parental assent were obtained from the participants after they received explanations about the possible risks, benefits, issue of confidentiality, voluntarism, and purposes of the study. The study is in compliance with the principles of the declaration of Helsinki.

Results

A total of 247 women at their third trimester of pregnancy were recruited for this study, and 235 of them were included in the final analysis, yielding a retention rate of 95.1%. Meanwhile, 111 (47.2%) and 124 (52.8%) mothers in the third trimester of pregnancy were included in the vigorous and moderate/low physical activity groups, respectively.

Socioeconomic characteristics of the mothers

The socioeconomic characteristics of the mothers are presented in Table 1. The mean age of the respondents was 29.1 years (SD: 5.4), ranging from 17 to 45 years. Most (71.1%) of them were rural residents, and 18.6% gave birth to a LBW baby. Over three-quarters (78.3%) of mothers were Muslim, and 152 (64.7%) belonged to the Gurage ethnic group. Nearly half (48.1%) of the mothers and 85 (36.2%) of their husbands had no formal education. Most (81.3%) of them used an improved drinking water source. The incidence of LBW significantly varied across age groups, with a higher incidence (28.0%) observed among the age group of 35 to 45 years (p = 0.02). Similarly, a significant variation was observed in the place of residence (p = 0.03), mothers’ level of education (p = 0.015), husbands’ level of education (p = 0.009), and water source (p = 0.015) between groups.

Table 1. Socioeconomic characteristics of pregnant women and the incidence of low birthweight in Butajira, Ethiopia.

Maternal characteristics	Total sample N (%)	Incidence of low birthweight n (%)	p-value ^a
Total	235 (100)	36 (15.3)
*Age (y)*
15–24	45 (19.1)	5 (11.1)	0.02
25–34	140 (59.6)	17 (12.1)
35–45	50 (21.3)	14 (28.0)
*Residence*
Rural	167 (71.1)	31 (18.6)	0.03
Urban	68 (28.9)	5 (7.4)	0.03
*Ethnicity*
Gurage	152 (64.7)	25 (16.4)	0.69
Silte	52 (22.1)	6 (11.5)
Others^**	31 (13.2)	5 (16.1)
*Formal education*
No	113 (48.1)	24 (21.2)	0.015
Yes	122 (51.9)	12 (9.8)	0.015
*Husbands’ formal education*
No	85 (36.2)	20 (23.5)	0.009
Yes	150 (63.8)	16 (10.7)	0.009
*Water source*
Improved	191 (81.3)	24 (12.6)	0.015
Non-improved	44 (18.7)	12 (27.3)	0.015
*Wealth quintile*
Lowest	47 (20.0)	7 (14.9)	0.845
Second	48 (20.4)	9 (18.6)
Middle	46 (19.6)	8 (17.4)
Fourth	47 (20.0)	7 (14.9)
Highest	47 (20.0)	5 (10.6)

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*Other = Catholic, Protestant, and other traditional religions

**Other = Oromo, Amhara, Wolayta, and Hadiya

^aPearson’s chi-square test

Mothers’ obstetric history, behavioral characteristics, and anthropometric measurement

Table 2 displays the obstetric history, behavioral and anthropometric characteristics of the mother and the incidence of low birthweight. Most (84.3%) of the mothers were multigravida, 130 (65.7%) had three or more children, and 23 (9.8%) had a history of miscarriage in their lifetime. More than two-fifths (42.9%) gave birth within an interval of 23 months or less. The vast majorities (90.6%) of mothers attended at least one ANC follow-up, and 176 (74.9%) took iron and folic acid supplementation. Almost all (97.4%) of the mothers consumed coffee, and 79 (33.6%) consumed khat (Catha Edulis). Mothers with a history of miscarriage had a significantly higher incidence of LBW (34.8%) than those who did not have a history of miscarriage (13.2%) (p < 0.01). Similarly, the incidence varied depending on the use of ANC (p < 0.05) and iron and folic acid supplementation (p < 0.001). Nearly one-fifth (18.3%) of the mothers had a height of less than 155 cm, and 50 (21.3%) had a MUAC of less than 23 cm. Eleven (4.7%) mothers weighed less than 50 kg, and 25 (10.6%) gained less than 7 kg during pregnancy. The incidence of LBW varied with maternal height (p = 0.04), MUAC (p = 0.02), and pre-pregnancy weight (p = 0.04).

Table 2. Obstetric and behavioral characteristics of pregnant women in their third trimester in Butajira Ethiopia.

Obstetric and behavioral characteristics	Total sample N (%)	Incidence of LBW n (%)	p-value
Total	235 (100)	36 (15.3)
*Gravidity* ^a
Multigravida	198 (84.3)	31 (15.7)	0.740
Primigravida	37 (15.7)	5 (13.5)	0.740
*Parity (n = 198)*^a
1–2 children	68 (34.3)	9 (13.2)	0.498
≥3 children	130 (65.7)	22 (16.9)	0.498
*History of miscarriage* ^a
Yes	23 (9.8)	8 (34.8)	0.060
No	212 (90.2)	28 (13.2)	0.060
*Birth interval (months) (n = 196)*^a
<23	84 (42.9)	15 (17.9)	0.498
≥24	112 (57.1)	16 (14.3)	0.498
*Antenatal care*^a
Yes	213 (90.6)	29 (13.6)	0.024
No	22 (9.4)	7 (31.8)	0.024
*Iron folic acid supplement* ^a
Yes	176 (74.9)	18 (10.2)	<0.001
No	59 (25.1)	18 (30.5)	<0.001
*Coffee consumption* ^b
Yes	229 (97.4)	35 (15.3)	0.926
No	6 (2.6)	1 (16.7)	0.926
*Khat^$ chewing* ^a
Yes	79 (33.6)	13 (16.5)	0.731
No	156 (66.4)	23 (14.7)	0.731
*Maternal height (cm)* ^a
<155	43 (18.3)	11 (25.6)	0.039
≥155	192 (81.7)	25 (13.0)	0.039
*Maternal mid-upper arm circumference* ^a
<23	50 (21.3)	13 (26.0)	0.018
≥23	185 (78.7)	23 (12.4)	0.018
*Pre-pregnancy weight (n = 61)* ^b
<50 kg	11 (4.7)	3 (27.3)	0.035
50–60 kg	41 (17.4)	2 (4.9)
≥60 kg	9 (3.8)	0 (0.0)
*Gestational weight gain* ^b
≤7 kg	25 (10.6)	3 (12.0)	0.1958
8–12 kg	20 (8.5)	0 (0.0)
>12 kg	5 (2.1)	1 (25.00)

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^$ Catha edulis

^aPearson’s chi-square test

^bFisher’s exact test

Food types and consumption frequency

The food consumption frequency of mothers during pregnancy is summarized in Table 3. Majority (91.1%) and 29 (12.3%) of the mothers consumed cereal and enset (Ensete ventricosum)-based food, respectively, at least once a day. More than half (56.6%) and 24 (10.2%) of them consumed vegetables and fruits at least once a day. A total of 106 (45.1%) and 62 (26.4%) of them consumed meat and milk products, respectively, less than once a month. More than two-fifth (41.7%) and 53 (22.6%) of them consumed egg and legumes, respectively, at least once a day. No significant association was observed in the incidence of LBW and consumption of various foods groups.

Table 3. Food consumption frequency among pregnant women in their third trimester in Butajira, Ethiopia.

Food items	Total sample N (%)	Incidence of LBW n (%)	p-value
Total	235 (100.0)	36 (15.3)
*Cereals and bread* ^a
≥once/day	214 (91.1)	30 (14.0)	0.077
<once/day	21 (8.9)	6 (28.6)	0.077
*Enset based* ^a
≥once/day	29 (12.3)	5 (17.2)	0.8598
4–6 times/week	15 (6.4)	2 (13.3)
2–3 times in a week	33 (14.0)	5 (15.2)
Once in a week	76 (32.3)	14 (18.4)
Twice or less in a month	82 (34.9)	10 (12.2)
*Vegetables* ^a
≥once/day	133 (56.6)	19 (14.3)	0.090
4–6 times/week	43 (18.3)	11 (25.6)
2–3 times/week	59 (25.1)	6 (10.2)
*Fruits* ^b
≥once/day	24 (10.2)	2 (8.3)	0.4007
4–6 times/week	44 (18.7)	7 (15.9)
2–3 times/week	38 (16.2)	4 (10.5)
Once a week	46 (19.6)	11 (23.9)
Once a month	31 (13.2)	3 (9.7)
<1 in a month	42 (17.9)	9 (21.4)
*Meat* ^b
≥once/day	13 (5.5)	2 (15.4)	0.2743
4–6 times/week	28 (11.9)	2 (7.1)
Once a week	33 (14.0)	3 (9.1)
1–2 times/month	55 (23.4)	7 12.7()
<1 in a month	106 (45.1)	22 (20.8)
*Egg* ^a
≥once/day	98 (41.7)	15 (15.3)	0.9963
2–3 times/week	137 (58.3)	21 (15.3)	0.9963
*Legumes* ^b
≥once/day	53 (22.6)	10 (18.9)	0.054
4–6 times/week	4 (1.7)	2 (50.0)
2–3 times/week	70 (29.8)	5 (7.1)
Once /week	18 (7.7)	3 (16.7)
1–2 times/month	20 (8.5)	2 (10.0)
<1 in a month	51 (21.7)	14 (27.5)
**Milk, cheese, and yoghurt** ^a
≥once/day	41 (17.4)	2 (4.9)	0.1908
2–3 times/week	75 (31.9)	15 (20.0)
1–2 times/month	57 (24.3)	9 (15.8)
<1 in a month	62 (26.4)	10 (16.1)
*Oils and fat* ^a
≤once/day	173 (73.6)	26 (15.0)	0.7634
2–3 times/week	31 (13.2)	4 (12.9)
Once in a week	31 (13.2)	6 (19.4)
*Sweets* ^a
>once/day	52 (22.1)	8 (15.4)	0.9795
4–6 times/week	67 (28.5)	11 (16.4)
2–3 times/week	44 (18.7)	7 (15.9)
Once in a week	72 (30.6)	10 (13.9)

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a = Pearson’s chi-square test

b = Fisher's exact test

Physical activity level and incidence of low birthweight

A total of 111 (47.2%) mothers were engaged in vigorous physical activities during their third trimester. The mean birthweight for newborns of mothers in the vigorous physical activity group was 2,917 grams (SD: 472), while that of newborns of mothers in the moderate or low physical activity group was 3,024 (SD: 376) grams. The incidence of LBW was significantly higher among mothers in the vigorous activity group 24 (21.6%) than moderate or low activity group 12 (9.7%) (p = 0.011). A total of 63 (26.8%) and 34 (14.5%) mothers had history of squatting and standing for longer hours, respectively, in their third trimester. The incidence of LBW was higher in those who stood for longer time (p = 0.013) and squatted (p = 0.009). The incidence of LBW was 25 (21.2%) and 4 (14.3%) in mothers who walked more than 60 minutes and below 30 minutes per day, respectively (p = 0.217). With regard to the level of sedentary behavior and sleeping, 34 (94.4%) and 26 (72.2%) of the mothers who gave birth to LBW babies were those who sat or reclined for <165 minutes per day (15.7%) and slept ≥8 hours (16.4%), respectively.

Multivariable analysis of physical activity and other determinants of low birthweight

To identify the independent effects of pattern and intensity of physical activity level on LBW, we employed a multivariable logistic regression model. It showed that the incidence of LBW significantly varied according to the level of vigorous physical activity level, standing for longer hours, walking, and squatting during the third trimester. As expected, water source and iron and folic acid supplementation were also significantly associated with LBW. The probability of LBW was 2.5 times higher for mothers who were involved in vigorous physical activities during the third trimester than those involved in moderate or low physical activities [AOR = 2.48, 95% CI: 1.01–6.09]. Similarly, the likelihood of LBW was 3.4 times higher for mothers who were involved in activities that require prolonged standing than those who were not involved in these types of activities [AOR = 3.37, 95% CI: 1.14–9.93]. The risk of LBW was 2.6 times higher in mothers who performed squatting in their third trimester than those who did not perform squatting [AOR = 2.61, 95% CI: 1.04–6.54]. (Table 4)

Table 4. Bivariable and multivariable analysis of the association of physical activity, sociodemographic, and reproductive health characteristics with low birth weight in South Ethiopia.

Variable	Low birthweight		COR [95% CI]	AOR [95% CI]
Variable	Yes n (%)	No n (%)	COR [95% CI]	AOR [95% CI]
*Age group (y)*
15–24	5 (11.1)	40 (88.9)	0.90 [0.31–2.61]	1.08 [0.33–3.51]
25–34	17 (12.1)	123 (87.9)	1	1
35–45	14 (28.0)	36 (72.0)	2.81 [1.26–9.49]	2.36 [0.82–6.75]
*Residence*
Rural	31 (18.6)	136 (81.4)	2.87 [1.06–7.73]	2.07 [0.60–7.05]
Urban	5 (7.4)	63 (92.6)	1	1
*Educational status*
Illiterate	24 (21.2)	89 (78.8)	2.47 [1.17–5.22]	0.92 [0.32–2.61]
Literate	12 (9.8)	110 (90.2)	1	1
*Husband’s educational status*
Illiterate	20 (23.5)	65 (76.5)	2.58 [1.25–5.30]	1.98 [0.92–4.99]
Literate	16 (10.7)	134 (89.3)	1	1
*Water source*
Improved	24 (12.6)	167 (87.4)	1	1
Unimproved	12 (27.3)	32 (72.7)	2.60 [1.18–5.74]	3.16 [1.17–8.52]^*
*Iron folic acid supplementation*
Yes	18 (10.2)	158 (89.8)	1	1
No	18(30.5)	41 (69.5)	3.85 [1.84–8.06]	6.13 [2.53–14.84]^*
*Mid-upper arm circumference*
<23	13 (26.0)	37 (74.0)	2.47 [1.15–5.33]	2.01 [0.87–6.21]
≥23	23 (12.4)	162 (87.6)	1	1
*Physical activity level*
Vigorous activity	24 (21.6)	87 (78.4)	2.57 [1.21–5.43]	2.48 [1.01–6.09]^*
Moderate activity	12 (9.7)	112 (90.3)	0.10 [0.05–0.19]	1
*Standing for longer hours*
Yes	10 (29.4)	24 (70.6)	2.80 [1.20–6.52]	3.37 [1.14–9.93]^*
No	26 (12.9)	175 (87.1)	1	1
*Squatting*
Yes	16 (25.4)	47 (74.6)	2.58 [1.24–5.39]	2.61 [1.04–6.54]^*
No	20 (11.6)	152 (88.4)	1	1

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*Statistically significant association at p < 0.05

Discussion

The sustainable development goal targeted to reduce neonatal mortality to at least 12 per 1,000 live births by 2030. Likewise, the Global Nutrition Target also aimed to achieve a 30% reduction in the number of infants born with a weight lower than 2,500 gm by the year 2025. As part of the LBW reduction strategy, it is indispensable to identify the risk factors linked to it in order to develop a targeted intervention. With this background information, we conducted a prospective cohort study among pregnant women engaged in physical activity during their third trimester, to determine the magnitude and its attributors on the incidence of LBW.

Based on our study, the incidence of LBW was 15.32%, which is consistent with the 2016 EDHS national estimate [13]. Moreover, other related studies in the country reported a LBW incidence of 13%–16.5% [10, 25, 26]. Our estimate is lower than that obtained from previous studies performed in countries with a documented prevalence of 22–54% [27–29]. Such discrepancies were expected since most of the above studies were facility based and targeted the high-risk groups. Compared with some previous studies conducted in Gondar and Jimma cities [30, 31], the values observed in the present study were higher due to the variations across geographical settings and seasonality. A recent systematic review performed in Ethiopia documented a pooled estimate of 17.3%, which is slightly higher than our findings [14], suggesting that LBW remains an important public health problem in the country.

In our study, 47.2% of mothers were involved in vigorous physical activities at work or home, and a significant proportion of them took part in activities that required squatting and standing for longer hours during their third trimester. Moreover, being involved in high intensity physical activity along with the warm weather would consequently lead to small for gestational age fetus and low birthweight [32].

In the multivariable analysis, engaging in vigorous intensity physical activities, prolonged standing, squatting during the third trimester, using unimproved water sources, and not taking iron supplements during pregnancy were significant determinants of LBW at term. The incidence of LBW was higher among mothers involved in vigorous activities, and our finding is concordant with McCowan et al.’s findings who documented that daily vigorous physical activity is associated with higher risk of LBW [33]. Bisson et al. also reported a 19.8 gram reduction in birthweight for one metabolic equivalent of task (MET)/hours/week increment spent in any vigorous exercise [32]. Moreover, Magann and his colleagues showed that women who engaged in heavy exercise had smaller (86.5 g) infants than sedentary women, which again emphasizes how vigorous activities affect birthweight [34]. By contrast, few studies indicated no significant effect of vigorous physical activity on birthweight [35–37]. These findings need to be interpreted cautiously since these studies assessed the effects of planned physical activity alone, which was 2 to 3 times per week for not more than 1 hour.

Mothers involved in activities that require prolonged standing were also more likely to have LBW neonates, and this finding is in congruence with the systematic review report, which showed that uninterrupted standing increased the odds of LBW threefold [38]. Increase in the activity of the sympathetic nervous system in active muscles, following prolonged standing results in the return of blood from visceral arteries to active muscles, increased sweating, decreased plasma volume, and reduced perfusion of blood to uterine and placental arteries [39].

The odds of having LBW was higher among mothers who performed squatting and is again in line with the findings of the Thailand and Indian studies, which showed that women who performed activities in squatting position were more likely to give birth to LBW babies [40, 41].

Using water from non-improved source was found to increase the odds of LBW babies, and similar finding was reported by a study from Ghana, which documented that living in a community with low coverage of safe water supply is associated with a high prevalence of LBW [42]. It is likely that mothers who do not have improved water supply at their locality might travel far to bring water. This causes physical strain that could result in low gestational weight gain, a known risk factor for LBW birth.

Mothers who did not receive iron supplements during pregnancy were more likely to have LBW babies. Our result is consistent with some previous studies conducted in Ethiopia [10, 43] and Nepal [44] that showed that by supplementing mothers with iron and other micronutrients, the risk of LBW could be reduced. This is sufficient evidence to support the fact that iron folic acid supplementation is associated with normal birthweight [45].

The following limitations need to be considered when interpreting the findings of this study. First, the use of self-reported physical activity could lead to subjective memory and reporting variations. However, as the variation is non-differential, i.e., it is not dependent on the outcome, the effect size estimate will not be biased. Second, we did not estimate the MET; hence, we could not measure the amount of reduction in birthweight for every unit increase in MET. Third, due to practical difficulty, we did not measure the exact amount of food servings consumed. However, the relative food frequency indicates minimal or no variation in food intake between study groups. Fourth, due to low educational status, only 25% of women reported pre-pregnancy weight. Thus, we could not adjust for pre-pregnancy BMI. Finally, we did not estimate the pregnancy weight gain at each trimester of pregnancy, which might have an impact on birthweight. However, as pregnancy weight gain might be in the causal pathway, controlling for it could lead to a biased estimate. Therefore, we believe that the effect size for vigorous physical activity is still valid.

Conclusion

The incidence of LBW in Ethiopia is considerably high. A significant proportion of women continue engaging in activities requiring vigorous physical effort, prolonged standing and squatting during the span of their pregnancy. These activities were found to be significantly associated with LBW in their babies. Lack of access to an improved water source and poor iron folic acid supplement utilization were linked with LBW. Therefore, health professionals working in maternity units should perform counseling regarding the recommended level of physical activity in each trimester of pregnancy. Moreover, the National Nutrition Program needs to improve the optimal dose of iron folic acid supplementation for pregnant women. Further research with a larger sample size and objective measurement of physical activity in each trimester is recommended.

Supporting information

S1 Table. STROBE statement—checklist of items for cohort studies.

(DOCX)

Click here for additional data file.^{(29.6KB, docx)}

S1 File. The English and Amharic version of the questionnaire used in this study.

(PDF)

Click here for additional data file.^{(1.2MB, pdf)}

S1 Dataset. The minimal dataset of the study.

(ZIP)

Click here for additional data file.^{(18.4KB, zip)}

Acknowledgments

The authors would like to thank the Butajira Health and Demographic Surveillance Site for their cooperation. Moreover, we would like to thank village informants for their cooperation in identifying pregnant women. We are also grateful to all study participants for their willingness to participate in the study.

Data Availability

The data underlying the results presented are uploaded as Supporting Information.

Funding Statement

ML has received partial financial support from Addis Ababa University for data collection. All funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. There was no additional external funding received for this study.

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PLoS One. doi: 10.1371/journal.pone.0236136.r001

Decision Letter 0

Frank T Spradley

18 May 2020

PONE-D-20-09704

Level of physical activity during the third trimester of pregnancy and its association with birthweight at term in South Ethiopia: A prospective cohort study

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Reviewer #1: Thank you for the opportunity to review this paper. The paper examines the relationship between physical activity and low birth weight in a cohort of women in Ethiopia. The topic is important as LBW is a significant contributor to newborn mortality and morbidity and had longer impacts on childhood growth and development.

More detail is needed in a number of areas.

What gestation were women recruited? The third trimester is too broad and better clarity is needed. How was the gestation determined and how sure are the authors of the accuracy of the gestation?

The inclusion states that women with a preterm baby and multiple birth were excluded. How were multiple births determined? Does the preterm birth comment mean women with a history of previous preterm birth were excluded as whether they will have a preterm birth cannot be known at this point?

Clarity about when the physical activity was taken from is needed. Many women do slow down towards the end of pregnancy so their activity level in early pregnancy may be different to late pregnancy. These things are not statistic necessarily. Was this accounted for at all?

In the analysis section, a clearer explanation of how the variable for the multivariate analysis were selected is needed. What was the cut off point? Which ones were initially included and then removed?

Parity does not seem to have had much attention. This is important as it is associated with a number of important issues including anaemia. Why was it not included in the multivariate analysis?

Abortion is included which is important. Is this spontaneous abortion which would be better mentioned as a miscarriage or an induced abortion? The long term implications of these two are different and so need to be clarified.

BMI is a common measure in studies like this but I cannot see this included.

The food consumption analysis is comprehensive but not easy to interpret. There are also too many individual comparisons related to fruit and vegetables etc consumed. Can these data be summarized into adequate diet versus not adequate diet?

There are more than 30 individual comparisons which makes the chance of finding an error when one does not really exist high, especially given the sample size. Can the authors comment on the power of the study given the number of comparisons and the possibly of statistical error?

The multivariate analysis seems to be missing important issues – BMI in early pregnancy, parity, anaemia? Were interactions examined? It is possible that there is an interaction between physical activity, standing for long hours and squatting. Given these are the three outcomes with significant results further examination needs to occur.

Some of the language needs attention. For example, scant rather than scanty (line 76), women instead of patients (line 99) and gave birth to rather than delivered (line 180).

Reviewer #2: Comments to the authors

The manuscript reports a prospective cohort study addressing the association of the level of physical activity with birthweigh in Ethiopia, where there is a high incidence of low birthweigh, and women work and house conditions usually lead to high volumes and intensities of physical activity. The study is well designed, the methodology is well explained, and the paper is well written and with a good level of English. Every section contains the necessary information and they are well related to each other. Just a few comments and small corrections have been suggested:

OVERVIEW:

The study seems quite complete. However, even if physical activity is the main outcome, I believe the study covers much more than physical activity. The study provides additional information about how other factors may be associated with low birthweigh, such as socioeconomic, obstetric and behavioral characteristics, food consumption and iron and folic acid supplementation. Therefore, I would extend the title of the paper to show that other factors have been studied, for instance: “Level of physical activity and other maternal characteristics during the third trimester of pregnancy and its association with birthweight at term in South Ethiopia: A prospective cohort study”. If the suggestion is followed, I would also mention this in the abstract.

METHODS

- Please, explain when this study was carried out.

- Please, explain if the modified version of the global physical activity questionnaire was validated or published somewhere. Was the pilot test in Silte published?

- Does the questionnaire consider the intensity of the physical activity developed? Or was the intensity deduced according to the type of exercise? “The level of physical activity was classified as moderate activity, vigorous activity, leisure time activities, sitting/reclining, walking, and sleeping”. How were low intensity activities classified? Was taking for granted that all leisure time activities were low intensity activities?

- “We assessed the dietary habit of the mother using a food frequency questionnaire within a month, prior to the baseline survey”. Does the food questionnaire used reflect the food habits of the study population? Please, briefly clarify it, as it seems you did.

- “Depending on their engagement in daily physical activity, mothers were categorized into the moderate intensity physical activity group and vigorous intensity physical activity group”. Were low activity women classified as moderate? Or there were no women who developed a low quantity of physical activity? Please, clarify.

- Is it possible to include information about how much activity or intensity was considered to classify women as "moderate" or "vigorous"?

RESULTS

- Please, the first time ANC is mentioned (Mothers’ obstetric history, behavioral characteristics, and anthropometric measurement section), clarify what this means (antenatal consultation?).

- I strongly suggest adding Body Mass Index (BMI) in the anthropometric measurement. Given that you have the height and the pre-pregnancy weigh, it is easy to calculate it, and it could add additional information that may be more representative of the reality than only the height or the weigh by itself.

- I also suggest adding information about BMI in Table 2 to see whether there were more LBW babies among women in any of the BMI categories (maybe underweight?). Even if the aim of the study is to analyze the possible correlation of the level of physical activity with birtweight, the study seems quite complete and provides extra information about socioeconomic, obstetric and behavioral characteristics, and food consumption; therefore BMI could add additional information, since it usually have a strong relationship with physical exercise and nutrition.

- Please, change name of Table 2 (it has been called Table 1 by mistake).

- What was the reason why there is so little women with the information about gestational weight gain? It seem one of the reasons is because little women reported their pre-gestational weight. Please, explain it.

- Table 3: please, modify the order in the enset, vegetables consumption, fruits, legums and sweets rows (4-6 times/week before 2-3 times/week).

- Please, revise and correct the third sentence of the section called “Physical activity level and incidence of low birthweight”, It is mentioned that “The incidence of LBW was significantly higher among mothers in the vigorous activity group 12 (21.6%) than moderate 12 (9.7%) activity group (p = 0.011)”. I believe you mean 24 women in the vigorous activity group; otherwise the numbers do not fit.

- Please, add the statistical significance of the next sentence: “The incidence of LBW was 25 (21.2%) and 4 (11.1%) in mothers who walked more than 60 minutes and below 30 minutes per day, respectively (, ADD with no statistical significance? or the P value)”.

- Please, correct the location of the percentages in the last sentence of the “Physical activity level and incidence of low birthweight” section. It can be misunderstanded: “With regard to the level of sedentary physical activity, 34 (15.7% REMOVE) (ADD 94.4%) and 26 (16.4% REMOVE) (ADD 72.2%) of the mothers who gave birth to LBW babies were those who sat or reclined for <165 minutes per day (HERE 15.7%) and slept ≥8 hours (HERE 16.4%), respectively”.

- Please, do not refer to sleep as sedentary physical activity, since sleeping is not a type of physical activity.

- Please, correct the sentence in page 16, line 268: “The risk of LBW was 2.6 times higher in mothers who were in their third trimester (ADD: AND PERFORMED SQUATTING) than those who did not perform squatting”.

**********

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Reviewer #1: Yes: Caroline Homer

Reviewer #2: Yes: Marina Vargas-Terrones

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PLoS One. 2020 Jul 20;15(7):e0236136. doi: 10.1371/journal.pone.0236136.r002

Author response to Decision Letter 0

24 Jun 2020

Response to Reviewers

Ref.: PONE-D-20-09704

Level of physical activity during the third trimester of pregnancy and its association with birthweight at term in South Ethiopia: A prospective cohort study

PLOS ONE

I, on behalf of all authors, thank editors and reviewers for their valuable and constructive comments to improve the excellence of this paper. We revised the manuscript based on the comments from the editor and the reviewers. Here is point by point response for each comments and questions raised by editors and reviewers.

Editors

SPECIFIC ACADEMIC EDITOR COMMENTS: Thank you for submitting your manuscript. Two expert reviewers handled your manuscript. Although interest was found in your study, there were major comments that arose during review. A number of these comments relate to the need for clarification and expansion of several vague points throughout the manuscript. Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

Response:

If the article is accepted, we agree that the peer review history to be publicly available.

Response:

Thank you for your comment. We revised the manuscript and we hope that the revised version meets all the journal requirements.

Response:

The questionnaires (English and the local language – Amharic) are uploaded as supporting information.

Response:

We uploaded the minimal anonymized data-set as supporting information.

4. Thank you for stating in your Funding Statement:

Response:

Here is the updated funding statement;

“ML has received partial financial support from Addis Ababa University for data collection. All funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. There was no additional external funding received for this study.”

5. Please include a copy of Table 2 which you refer to in your text on page 11.

Response: Table 2 is available in page 12 of the revised manuscript.

Reviewer #1:

Thank you for the opportunity to review this paper. The paper examines the relationship between physical activity and low birth weight in a cohort of women in Ethiopia. The topic is important as LBW is a significant contributor to newborn mortality and morbidity and had longer impacts on childhood growth and development. More detail is needed in a number of areas.

1. What gestation were women recruited? The third trimester is too broad and better clarity is needed. How was the gestation determined and how sure are the authors of the accuracy of the gestation?

Response:

Thank you for your comment. We enrolled women in their 31 to 34 weeks of gestation. The gestational age was determined using the last menstrual period (LMP). We add a description in line 108-110 of the revised version. Since the participants are under ongoing pregnancy surveillance and the list was taken from it, the gestational age would not be affected to a large extent. Even if there is a possibility of mis-calculation of the GA, the effect size would not be affected due to non-differential for both exposed and unexposed groups.

2. The inclusion states that women with a preterm baby and multiple birth were excluded. How were multiple births determined? Does the preterm birth comment mean women with a history of previous preterm birth were excluded as whether they will have a preterm birth cannot be known at this point?

Response:

Thank you for your comment. We excluded those with previous pre-term baby before enrollment. As we didn’t have access to ultrasound, we had planned to exclude preterm birth and multiple birth from the analysis (not from enrollment-as we couldn’t confirm it with ultrasound). However, there was no multiple birth. There was 1 who delivered pre-term in the current pregnancy and was excluded from the analysis. To make it more clear, we revised it in the study design and analysis section.

3. Clarity about when the physical activity was taken from is needed. Many women do slow down towards the end of pregnancy so their activity level in early pregnancy may be different to late pregnancy. These things are not statistic necessarily. Was this accounted for at all?

Response:

All PA measurements taken during enrollment (31-34 weeks of gestation). The questionnaire measured the level of physical activity of the women in the last 7 days prior to data collection time. We described it in line 122-131 of the revised version.

4. In the analysis section, a clearer explanation of how the variable for the multivariate analysis were selected is needed. What was the cutoff point? Which ones were initially included and then removed?

Response:

A bivariable analysis was carried out to determine the crude association of predictor variables with birthweight, and based on the results, variables with p-value <0.05 were selected for multivariable analysis. The variable ANC follow up was excluded from the multivariable model due to collinearity with iron folic acid supplementation. We described it in line 163-168 of the revised manuscript.

5. Parity does not seem to have had much attention. This is important as it is associated with a number of important issues including anemia. Why was it not included in the multivariate analysis?

Response:

We agree with your concern. Gravidity and parity are presumed to be risk factors of low birthweight. However, in our sample their confounding effect is minimal. The p-value of both gravidity and parity during bivariate analysis was high (0.74 and 0.498 respectively) as presented in table 2, page 12. This doesn’t mean they are not risk factors, but, their confounding effect in our sample is very minimal. Therefore, we did not included them in the multivariate analysis. Hence, their impact on the association between physical activity and low birthweight in our sample is minimal.

6. Abortion is included which is important. Is this spontaneous abortion which would be better mentioned as a miscarriage or an induced abortion? The long term implications of these two are different and so need to be clarified.

Response:

It is spontaneous abortion or miscarriage. We revised it throughout the manuscript as miscarriage.

7. BMI is a common measure in studies like this but I cannot see this included.

Response:

We used mid-upper arm circumference (MUAC) and it is the good surrogate during late pregnancy (third trimester). Several studies recommended MUAC as an indicator of nutritional status of mother during pregnancy, especially for in such context, where mothers hardly monitor their pre-pregnancy and post-pregnancy weight.

8. The food consumption analysis is comprehensive but not easy to interpret. There are also too many individual comparisons related to fruit and vegetables etc. consumed. Can these data be summarized into adequate diet versus not adequate diet?

Response:

Thank you for your comment. We agree that, it would be better to have a more comprehensive composite measure like ‘adequate/inadequate’. However, we couldn’t categorize it to adequate and inadequate as we didn’t measure the exact amount of food they took. We just assessed the relative frequency of intake for each food items. The weighed food diaries were not practically feasible in our context. We admit this limitation and add a description in line 344-346 of the revised version.

9. There are more than 30 individual comparisons which makes the chance of finding an error when one does not really exist high, especially given the sample size. Can the authors comment on the power of the study given the number of comparisons and the possibly of statistical error?

Response:

Thank you for your concern. We agree that type one error might be inflated. However, since our main hypothesis is to see the association between physical activity and low birthweight, other variables were assessed to see the confounding effect. In the meantime, we reported variables that remain significant during multivariate analysis. The study is powered to detect to effect of PA on LBW. The power for other predictors may not be sufficient.

10. The multivariate analysis seems to be missing important issues – BMI in early pregnancy, parity, anemia? Were interactions examined? It is possible that there is an interaction between physical activity, standing for long hours and squatting. Given these are the three outcomes with significant results further examination needs to occur.

Response:

We used MUAC instead of BMI, as we described in the previous response. Regarding the pre-pregnancy or early pregnancy BMI, we used self-reported weight to compute gestational weight gain. However, the pre-pregnancy weight is prone to error due to low educational level of study participants. In addition, only 25% of women reported their pre-pregnancy weight. Regarding parity, we agree that it is a known risk factor. However, in our sample it is comparable in both groups and the bivariate analysis also showed that as we mentioned in the previous response. Therefore, the confounding effect is minimal in this study.

11. Some of the language needs attention. For example, scant rather than scanty (line 76), women instead of patients (line 99) and gave birth to rather than delivered (line 180).

Response:

Thank you for your suggestion. We revised the whole manuscript for grammar and spelling.

Reviewer #2:

The manuscript reports a prospective cohort study addressing the association of the level of physical activity with birthweight in Ethiopia, where there is a high incidence of low birthweight, and women work and house conditions usually lead to high volumes and intensities of physical activity. The study is well designed, the methodology is well explained, and the paper is well written and with a good level of English. Every section contains the necessary information and they are well related to each other. Just a few comments and small corrections have been suggested:

OVERVIEW:

1. The study seems quite complete. However, even if physical activity is the main outcome, I believe the study covers much more than physical activity. The study provides additional information about how other factors may be associated with low birthweight, such as socioeconomic, obstetric and behavioral characteristics, food consumption and iron and folic acid supplementation. Therefore, I would extend the title of the paper to show that other factors have been studied, for instance: “Level of physical activity and other maternal characteristics during the third trimester of pregnancy and its association with birthweight at term in South Ethiopia: A prospective cohort study”. If the suggestion is followed, I would also mention this in the abstract.

Response:

Thank you for your suggestion. We agree that other relevant determinants are also studied. We accept the suggestion and we mentioned it in the title and abstract.

METHODS

2. Please, explain when this study was carried out.

Response:

Thank you for your comment. We added the information that the study was conducted from January to June 2017 in line 88-89 of the revised version.

3. Please, explain if the modified version of the global physical activity questionnaire was validated or published somewhere. Was the pilot test in Silte published?

Response:

No, the pilot test is not published. The GPAQ is already internationally validated standard questionnaire. We customized it for the types of activities specific to the context of the study area. We performed an internal consistency test using the pilot data, and results showed acceptable level (Cronbach’s alpha = 0.79). We mentioned it in line 137-141 of the revised manuscript.

4. Does the questionnaire consider the intensity of the physical activity developed? Or was the intensity deduced according to the type of exercise? “The level of physical activity was classified as moderate activity, vigorous activity, leisure time activities, sitting/reclining, walking, and sleeping”. How were low intensity activities classified? Was taking for granted that all leisure time activities were low intensity activities?

Response:

Thank you for your comment. The intensity is estimated according to the type of exercise. Regarding leisure time activities, it is editing problem. Leisure time activities are not part of the level of physical activities rather the domain or the type of activities. As you said leisure time or recreational activities could also be vigorous. We also divided leisure time into vigorous and moderate. For instance, running continuously for at least for 10 minutes is considered as vigorous despite it is recreational. We revised it in line 124-129 of the method section. For more information, we uploaded the study questionnaires as supporting information.

5. “We assessed the dietary habit of the mother using a food frequency questionnaire within a month, prior to the baseline survey”. Does the food questionnaire used reflect the food habits of the study population? Please, briefly clarify it, as it seems you did.

Response:

Thank you for your comment. We assessed the usual intake and frequency of food intake during pregnancy. In general, Food Frequency Questionnaires (FFQ) can be asked 1 month, 3 month, 6 month, 1 year or 5 year prior to the data collection time depending on the aim of the study. Usually chronic disease studies use one or five year dietary history in order to assess the long term impact of diet. However, in our case we were concerned on the dietary habit during pregnancy. Therefore, we used dietary history of 1 month prior to the data collection point. 1 month is preferable in a situation like us to minimize recall bias. We revised it in line 131-134 of the revised version.

6. “Depending on their engagement in daily physical activity, mothers were categorized into the moderate intensity physical activity group and vigorous intensity physical activity group”. Were low activity women classified as moderate? Or there were no women who developed a low quantity of physical activity? Please, clarify.

Response:

Thank you for your comment. There were few women who had low intensity physical activity and were categorized as moderate PA level. Since our aim was to assess the impact of vigorous physical activity on low birthweight, we considered those who do not have vigorous activity as one group (both moderate and low). We add more descriptions in line 128-130 of the revised version.

7. Is it possible to include information about how much activity or intensity was considered to classify women as "moderate" or "vigorous"?

Response:

We used the WHO GPAQ guideline. We ask them “Does your work involve vigorous-intensity activity that causes large increases in breathing or heart rate?” by showing them cards to specific activity types such as carrying, loading or stacking wood; chopping wood-splitting logs; manual grinding; drawing water from the well, river, etc. Similarly for leisure time physical activities. We then categorized those who do any type of vigorous activities in one group and those who do not in another group. The type of vigorous activities reported were predominantly work related activities.

RESULTS

8. Please, the first time ANC is mentioned (Mothers’ obstetric history, behavioral characteristics, and anthropometric measurement section), clarify what this means (antenatal consultation?).

Response:

Thank you for your comment. We write it in long form in its first appearance.

9. I strongly suggest adding Body Mass Index (BMI) in the anthropometric measurement. Given that you have the height and the pre-pregnancy weight, it is easy to calculate it, and it could add additional information that may be more representative of the reality than only the height or the weight by itself.

Response:

Thank you for your comment. We also agree that BMI could have additional information. However, only 25% of women reported their pre-pregnancy weight. On the other hand, using self-reported pre-pregnancy weight to calculate pre-pregnancy BMI is somehow prone to error. The main reason to ask pre-pregnancy weight was to estimate the gestational weight gain. Instead, We used mid-upper arm circumference (MUAC), and it is a good surrogate during late pregnancy (third trimester).

10. I also suggest adding information about BMI in Table 2 to see whether there were more LBW babies among women in any of the BMI categories (maybe underweight?). Even if the aim of the study is to analyze the possible correlation of the level of physical activity with birthweight, the study seems quite complete and provides extra information about socioeconomic, obstetric and behavioral characteristics, and food consumption; therefore BMI could add additional information, since it usually have a strong relationship with physical exercise and nutrition.

Response:

Thank you for your comment. We agree that including BMI might be additional information. If the pre-pregnancy weight and height was measured by the data collectors, it would have been reasonable to use it. However, due to the pre-pregnancy weight is self-reported, it is prone to error as the women in the study population has relatively low level of education. Only 25% of women reported their pre-pregnancy weight, which make using BMI less reliable. The self-reported weight is a simple rough estimate. Moreover, the height is measured during enrollment, using self-reported pre-pregnancy weight and height during 3rd trimester would have flawed results. Instead, we used MUAC measured by trained data collectors, which we think it is acceptable during pregnancy.

11. Please, change name of Table 2 (it has been called Table 1 by mistake).

Response:

Thank you for your comment. We revised it accordingly.

12. What was the reason why there is so little women with the information about gestational weight gain? It seem one of the reasons is because little women reported their pre-gestational weight. Please, explain it.

Response:

Yes, due to low educational status of women in the study area, it is rare for them to measure and monitor their weight. That is the reason we do not use pre-pregnancy BMI. We described in line 348-349 of the revised version.

13. Table 3: please, modify the order in the enset, vegetables consumption, fruits, legums and sweets rows (4-6 times/week before 2-3 times/week).

Response:

Thank you for your comment. We revised it accordingly.

14. Please, revise and correct the third sentence of the section called “Physical activity level and incidence of low birthweight”, It is mentioned that “The incidence of LBW was significantly higher among mothers in the vigorous activity group 12 (21.6%) than moderate 12 (9.7%) activity group (p = 0.011)”. I believe you mean 24 women in the vigorous activity group; otherwise the numbers do not fit.

Response:

Thank you for your feedback. Yes, it is 24 (21.6%).

15. Please, add the statistical significance of the next sentence: “The incidence of LBW was 25 (21.2%) and 4 (11.1%) in mothers who walked more than 60 minutes and below 30 minutes per day, respectively (, ADD with no statistical significance? or the P value)”.

Response: Thank you for your comment. We added p-value though not statistically significant.

16. Please, correct the location of the percentages in the last sentence of the “Physical activity level and incidence of low birthweight” section. It can be misunderstanded: “With regard to the level of sedentary physical activity, 34 (15.7% REMOVE) (ADD 94.4%) and 26 (16.4% REMOVE) (ADD 72.2%) of the mothers who gave birth to LBW babies were those who sat or reclined for <165 minutes per day (HERE 15.7%) and slept ≥8 hours (HERE 16.4%), respectively”.

Response:

Thank you for your comment. We re-arranged the percentages.

17. Please, do not refer to sleep as sedentary physical activity, since sleeping is not a type of physical activity.

Response:

Thank you for your comment. We separated ‘sleep’ from sedentary lifestyle throughout the manuscript.

18. Please, correct the sentence in page 16, line 268: “The risk of LBW was 2.6 times higher in mothers who were in their third trimester (ADD: AND PERFORMED SQUATTING) than those who did not perform squatting”.

Response:

Thank you for your comment. We revised it accordingly.

With regards,

Hamid Y. Hassen

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PLoS One. doi: 10.1371/journal.pone.0236136.r003

Decision Letter 1

Frank T Spradley

30 Jun 2020

Level of physical activity and other maternal characteristics during the third trimester of pregnancy and its association with birthweight at term in South Ethiopia: A prospective cohort study

PONE-D-20-09704R1

Dear Dr. Hassen,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Academic Editor

PLOS ONE

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: I Don't Know

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #1: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #1: Yes

**********

6. Review Comments to the Author

Reviewer #1: The authors have addressed my comments mostly. I still have two problems with the paper though - the way diet is reported which is very hard to interpret and the very many comparisons mean that it is possible that differences were found by chance.

The other problem is the possible interaction between the some of the activities which I explained in my initial review. I still have concerns that the activities are not mutually exclusive.

The authors have addressed these but I am not sure their actual design makes it possible to completely address these issues.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Caroline Homer

PLoS One. doi: 10.1371/journal.pone.0236136.r004

Acceptance letter

Frank T Spradley

6 Jul 2020

PONE-D-20-09704R1

Level of physical activity and other maternal characteristics during the third trimester of pregnancy and its association with birthweight at term in South Ethiopia: A prospective cohort study

Dear Dr. Hassen:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Frank T. Spradley

Academic Editor

PLOS ONE

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

S1 Table. STROBE statement—checklist of items for cohort studies.

(DOCX)

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S1 File. The English and Amharic version of the questionnaire used in this study.

(PDF)

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S1 Dataset. The minimal dataset of the study.

(ZIP)

Click here for additional data file.^{(18.4KB, zip)}

Attachment

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Data Availability Statement

The data underlying the results presented are uploaded as Supporting Information.

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PERMALINK

Level of physical activity and other maternal characteristics during the third trimester of pregnancy and its association with birthweight at term in South Ethiopia: A prospective cohort study

Meseret Legesse

Jemal Haider Ali

Md Dilshad Manzar

Mohammed Salahuddin

Hamid Yimam Hassen

Roles

Abstract

Introduction

Methods and materials

Study setting

Study design and study participants

Sample size and sampling procedure

Data collection procedure

Data quality control measures

Definition of terms

Statistical methods

Participant consent and ethical approval

Results

Socioeconomic characteristics of the mothers

Table 1. Socioeconomic characteristics of pregnant women and the incidence of low birthweight in Butajira, Ethiopia.

Mothers’ obstetric history, behavioral characteristics, and anthropometric measurement

Table 2. Obstetric and behavioral characteristics of pregnant women in their third trimester in Butajira Ethiopia.

Food types and consumption frequency

Table 3. Food consumption frequency among pregnant women in their third trimester in Butajira, Ethiopia.

Physical activity level and incidence of low birthweight

Multivariable analysis of physical activity and other determinants of low birthweight

Table 4. Bivariable and multivariable analysis of the association of physical activity, sociodemographic, and reproductive health characteristics with low birth weight in South Ethiopia.

Discussion

Conclusion

Supporting information

Acknowledgments

Data Availability

Funding Statement

References

Decision Letter 0

Frank T Spradley

Roles

Author response to Decision Letter 0

Decision Letter 1

Frank T Spradley

Roles

Acceptance letter

Frank T Spradley

Roles

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

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