ABSTRACT
Background:
The majority of all low birth weight (LBW) babies are born in developing countries, and half of the population in developing nations use solid fuels as their primary source of energy for cooking. An association between household use of solid biomass fuels and reduced newborn weight has been found in several countries. India has a high prevalence of LBW babies, and 88% of the population use solid fuels for cooking.
Objectives:
To evaluate the determinants of low birth weight and to assess the effect of exposure of pregnant women to indoor air pollution on the birth weight of newborns.
Methodology:
A case–control study was conducted on singleton newborn babies of KIMS hospital, Hubballi. A structured pretested validated questionnaire was administered to 146 participants including 73 cases (new born babies with birth weight <2.5 kg) and 73 controls (new born babies with birth weight ≥2.5k g). The questionnaire comprised of sociodemographic characteristics, obstetric history, medical illnesses, and the current pregnancy with its outcomes and indoor air pollution.
Results:
The study found a significant association between low birth weight and a history of low birth weight, no intake of albendazole tablets, hemoglobin levels during pregnancy, exposure to smoke from mosquito repellent coils during pregnancy, burning of volatile liquids at home, and duration of exposure to indoor air pollutants during pregnancy.
Conclusion:
Indoor air pollution significantly affects the baby’s birth weight. Appropriate antenatal care and health education to overcome indoor air pollution can significantly improve the birth weight of the baby.
Keywords: Indoor air pollution, low birth weight, mosquito repellents, volatile liquids
Introduction
Air pollution has become a serious concern for developing countries in terms of intensity of exposure, total exposure time, and number of people exposed. Approximately 76% of particulate matter air pollution around the world occurs indoor in developing countries.[1]
As of 2011, one-third of the world and 90% of the rural household population in developing countries were using solid fuel as a source of energy for domestic use.[2] In developing countries, where a large proportion of household rely on solid fuels for cooking, heating and lighting, concentration of air pollutants indoors tends to be high.[3] Traditional cooking stoves are typically simple, inefficient at combusting solid fuel and used mostly in unventilated households, which produce large volumes of indoor smoke.[4]
Significant amount of life-threatening air pollutant including particulate matter, formaldehyde, carbon monoxide, nitrogen oxide, benzene, hydrocarbons, and many other toxic organic compounds are produced because of burning solid fuel like wood, agricultural crops, animal dung, straw, shrubs, grass, and charcoal.[5] These air pollutants have long been speculated to have impact on infant birth weight, and potential mechanism includes oxidative stress, inflammation, coagulation, impaired endothelial function and hemodynamic responses, which might impair placental function and subsequently result in growth retardation, stillbirth, low birth weight or other adverse pregnancy outcomes.[6]
Low birth weight (LBW) is defined as weight of the new born at birth less than 2500 grams irrespective of gestational age.[7] Low birth weight is an important determinant of mortality, morbidity, and disability in infancy and childhood.[8] It has a long-term impact on health outcomes in adult life such as hypertension, diabetic nephropathy, proteinuria, progressive renal disease at late age, eye problems like strabismus and myopia, deafness, neurological complications like cerebral palsy, developmental delay with IQ less than 70%, epilepsy and behavioural disturbance.[9] Low birth weight also results in significant cost to the health sector and imposes a significant burden on society as a whole. The global prevalence of such births is slowly dropping; however, in developing countries, it is as high as 30%. The association between maternal exposure to household air pollution and low birth weight has been described in a number of studies.[10] Low birth weight is an existing public health problem requiring attention at the primary healthcare level. LBW is a critical public health issue that significantly impacts neonatal survival, growth, and long-term health. Understanding its determinants, particularly the role of indoor air pollution, is vital for strengthening primary health care services. Primary health care plays a pivotal role in addressing LBW through preventive measures, community-based interventions, and promoting awareness about clean cooking practices and maternal health. By integrating targeted strategies into primary health care, this study can contribute to reducing LBW incidence and improving maternal and child health outcomes at the grassroots level. However, only few studies have been conducted in this region of India to establish this association.
Hence, this study was conducted to evaluate the determinants of low birth weight and to assess the effect of exposure of pregnant women to indoor air pollution on birth weight of new born.
Methodology
This was a retrospective facility-based case–control study for a period of one month from July 2019 to August 2019. Based on the study conducted by S Ganesh Kumar et al.[11] at Manipal, the proportion of anaemia among cases was 53.6% and among controls was 22.1%, with an odds ratio of 3.11. Considering alpha error of 5% and 90% power of the study with 1:1 ratio for cases and controls. Final sample size was 146, of which 73 were cases and 73 were controls. Participants fulfilling the definition of cases and controls were selected by simple random sampling. Matching was done for gestational age and age of the mother. The ethical clearance was obtained from the Institutional Ethics Committee of KIMS, Hubballi, on 11th March 2019.
Definitions for cases and controls
Cases: singleton new born babies with birth weight <2.5 kg at term.
Controls: singleton new born babies who were at term with normal birth weight of ≥2.5 kg.
Exclusion criteria: new born identified with congenital anomalies at birth.
Study tool
A semistructured pretested questionnaire was used to collect patient’s information, comprised of the following parts:
Part 1 of the questionnaire obtained information about particulars of the participant.
Part II extracted information about various sociodemographic characteristics of the mother, obstetric history, history of medical illness, history of antenatal care for this pregnancy and outcomes of the pregnancy.
Part III included information about the exposure of mother to of indoor air pollutants during the pregnancy.
The questionnaire was administered to collect necessary information after taking informed consent. Information about the sociodemographic characteristics, obstetric history, outcome of the current pregnancy and indoor air pollution was collected. Data pertaining to investigations were extracted from the participants medical records. The data were collected from obstetrics ward, intensive care units and emergency obstetric ward (casualty) of the hospital.
Statistical analysis
Data were entered in Microsoft excel and analysed using Statistical Program for Social Sciences (SPSS) Version 21. Continuous data were expressed as mean and standard deviation. Categorical data were expressed as proportions. Student’s t test was used to test the significance of continuous variables. Categorical data were analysed using the Chi-square test. A P value of < 0.05 was considered significant. Variables with P value < 0.05 on univariate analysis were considered for multivariate logistic regression.
Results
The current study included 50.7% and 56.7% of the male babies among cases and controls, respectively [Table 1]. The mean years of spacing were 1.952 years and 2.151 years with standard deviation of 1.4462 and 1.9034, respectively. The majority of the babies were the first-order births [Table 2 (1)]. The mean levels of haemoglobin were 9.6 gm% and 10.08% among cases and controls, respectively [Table 2 (2)]. Most mothers reported using LPG for cooking purposes, and many of them reported using wood as the fuel for other domestic purposes [Table 3]. The factors found to be significantly associated with the low birth weight were low hemoglobin levels, nonadministration of albendazole during pregnancy, Rh status of the mother and mean duration of exposure to the indoor air pollutant [Table 4].
Table 1.
Sociodemographic characteristics of cases and controls
| Variables | Categories | Groups n (%) | Chi-square | P | |
|---|---|---|---|---|---|
|
| |||||
| Controls | Cases | ||||
| Religion | Hindu | 58 (79.5) | 47 (64.4) | 4.1036 | <0.05* |
| Muslim | 15 (20.5) | 26 (35.6) | |||
| Education | Illiterate | 5 (6.9) | 8 (10.9) | 0.76 | >0.05 |
| Literate | 68 (93.1) | 65 (89.1) | |||
| Occupation | Working | 5 (6.9) | 7 (9.6) | 0.3632 | >0.05 |
| Home Maker | 68 (93.1) | 66 (90.4) | |||
| Occupation of The Husband | Below Clerical | 67 (91.8) | 62 (84.9) | 1.6644 | >0.05 |
| Clerical And Above | 6 (8.2) | 11 (15.1) | |||
| Type of Family | Joint | 46 (62.9) | 47 (64.4) | 0.0296 | >0.05 |
| Nuclear | 27 (37.1) | 26 (35.6) | |||
| Residence | Urban | 17 (23.3) | 22 (30.1) | 0.8747 | >0.05 |
| Rural | 56 (76.7) | 51 (69.9) | |||
| Socioeconomic status | class III and above | 9 (12.3) | 6 (8.2) | 0.669 | >0.05 |
| class IV and V | 64 (87.7) | 67 (91.8) | |||
*Significant
Table 2 (1).
Maternal factors in low birth weight
| Variables | Group | Mean | Std. Deviation | Std. Error of Mean | t | P |
|---|---|---|---|---|---|---|
| Age | Case | 24.53 | 4.397 | 0.515 | 0.057 | >0.05 |
| Control | 24.49 | 4.298 | 0.503 | |||
| Spacing | Case | 1.952 | 1.446 | 0.169 | 0.71 | >0.05 |
| Control | 2.151 | 1.903 | 0.223 | |||
| Gestational Age | Case | 37.3 | 1.506 | 0.176 | 1.193 | >0.05 |
| Control | 36.66 | 2.405 | 0.281 | |||
| Weight Gain | Case | 8 | 2.115 | 0.248 | 1.4 | >0.05 |
| Control | 7.45 | 2.375 | 0.278 | |||
| ANC Visits | Case | 6.12 | 0.798 | 0.093 | 0.714 | >0.05 |
| Control | 6.27 | 1.618 | 0.189 | |||
| IFA Tablets | Case | 137.26 | 60.99 | 7.139 | 0.261 | >0.05 |
| Control | 134.52 | 65.89 | 7.712 | |||
| Haemoglobin Levels | Case | 9.634 | 1.35 | 0.158 | 2.11 | <0.05* |
| Control | 10.086 | 1.235 | 0.115 |
*Significant
Table 2 (2).
Maternal factors in low birth weight
| Variables | Categories | Groups | Chi-square | P | |
|---|---|---|---|---|---|
|
| |||||
| Controls | Cases | ||||
| Number of pregnancies (Gravida) | Multi | 28 (38.4) | 29 (39.7) | 0.02878 | >0.05 |
| Primi | 45 (61.6) | 44 (60.3) | |||
| Albendazole | Not taken | 28 (38.4) | 42 (57.5) | 5.37895 | <0.05* |
| Taken | 45 (61.6) | 31 (42.5) | |||
| Pregnancy Induced Hypertension | Present | 2 (2.7) | 3 (4.1) | 0.20709 | >0.05 |
| Absent | 71 (97.3) | 70 (95.9) | |||
| Sex of Baby | Male | 41 (56.2) | 37 (50.7) | 0.44042 | >0.05 |
| Female | 32 (43.3) | 36 (49.3) | |||
| RH status | Negative | 17 (23.3) | 8 (10.9) | 3.90942 | <0.05* |
| Positive | 56 (76.7) | 65 (89.1) | |||
*significant
Table 3.
Indoor air pollutants
| Variables | Categories | Groups | Chi-square | P | |
|---|---|---|---|---|---|
|
| |||||
| Controls | Cases | ||||
| Cooking fuel | Wood | 15 (20.6) | 24 (32.9) | 2.83393 | >0.05 |
| LPG | 58 (79.4) | 49 (63.1) | |||
| Wood for domestic purposes | Yes | 63 (86.3) | 66 (90.4) | 0.59918 | >0.05 |
| No | 10 (13.7) | 7 (9.6) | |||
| Gas geyser | Yes | 12 (16.4) | 14 (19.2) | 0.18718 | >0.05 |
| No | 61 (83.6) | 59 (80.8) | |||
| Use of mosquito repellent | Yes | 12 (16.4) | 28 (38.4) | 8.81509 | <0.05* |
| No | 61 (83.6) | 45 (61.6) | |||
| Use of volatile liquids | Yes | 21 (28.8) | 35 (47.9) | 5.67778 | <0.05* |
| No | 52 (71.2) | 38 (52.1) | |||
| Dung cakes | Yes | 13 (17.8) | 9 (12.3) | 0.85631 | >0.05 |
| No | 60 (82.2) | 64 (87.7) | |||
*significant
Table 4.
Duration of exposure to indoor air pollutant
| Groups | Mean hours of exposure/day | Std. Deviation | Std. Error Mean | t | P |
|---|---|---|---|---|---|
| Control | 1.5 | 0.8937 | 0.1046 | 4.146 | <0.001 |
| Case | 2.11 | 0.8829 | 0.1033 |
On multivariate logistic regression of the factors significant in univariate analysis, it was found that there were higher odds of low birth weight in mothers with low haemoglobin level, not taking albendazole during pregnancy, Rh-positive status of the mother, use of mosquito repellents inside the house and increased duration of exposure to indoor air pollutants [Table 5].
Table 5.
Multivariate logistic regression of maternal factors and indoor air pollutants
| Variables | AOR | 95% C. I. for AOR | P | |
|---|---|---|---|---|
|
| ||||
| Lower | Upper | |||
| Haemoglobin | 0.721 | 0.532 | 0.979 | <0.05 |
| Albendazole (not taken) | 2.921 | 1.325 | 6.439 | <0.05 |
| Rh status (positive) | 0.310 | 0.112 | 0.861 | <0.05 |
| Use of mosquito repellent | 2.625 | 1.087 | 6.337 | <0.05 |
| Using volatile liquids | 1.982 | 0.897 | 4.376 | >0.05 |
| Duration of exposure to pollutant | 2.056 | 1.313 | 3.220 | <0.01 |
Discussion
We conducted a case–control study on 73 cases and 73 controls to evaluate the determinants of low birth weight and role of indoor pollution on birth weight.
On univariate analysis, there was a significant difference [P < 0.05] between the mean HB levels of cases (9.63 gm%) and controls [10.086 gm%]. A study by Ganesh Kumar et al. in Mangalore and a study by Kotabal et al. in Shimogga showed a similar association with anemia and low birth weight.[11,12,13]
Low birth weight was found to be significantly associated with not taking albendazole tablet during pregnancy. Birth weight was significantly (P < 0.05) associated with blood transfusion during current pregnancy. This could be attributable to improved hemoglobin levels.
On assessing the role of various indoor air pollution, the factors that were significantly associated with low birth weight were the use of mosquito repellents inside the house [OR = 3.163 (1.452-6.88) P = 0.03] and the burning of a volatile liquid (kerosene) inside the house [OR = 2.281 (1.151-4.519) P = 0.017]. A study by Edith B Milanzi et al.[14] in Malawi showed a similar association of low birth weight with maternal exposure to biomass smoke during pregnancy.
There was a significant difference between mean duration of exposure to indoor air pollutant (smoke due to burning of wood, dung cake, LPG, geyser, Burning of volatile liquid, storage of pesticide inside the house, use of mosquito repellent) among cases (2.110 hrs) and controls (1.5 hrs).
On multivariate analysis, low haemoglobin level, not taking albendazole during pregnancy, Rh-positive status of the mother, use of mosquito repellents inside the house and increased duration of exposure to indoor air pollutants were significantly associated with low birth weight.
Another study found that severe anemia was a significant risk factor for low birth weight, which is a similar finding in the current study.[15]
A similar study by Patel et al.[16] reported that maternal anemia is a significant risk factor for low birth weight.
Conclusion
Measures to prevent anemia like albendazole administration, blood transfusion, and treatment of anemia during pregnancy have a significant impact on improving birth weight.
Indoor air pollution has a significant effect on birth weight of the baby. Hence, measures have to be taken to combat indoor air pollution and policies have to be made to improve indoor air quality.
Recommendation
Based on the current research, it is recommended that albendazole should be given to all pregnant women in the second trimester and anaemia should be treated using oral iron therapy in early trimesters and with parenteral iron therapy or blood transfusion in the third trimester to improve the birth weight of the baby.
Health education should be provided about the health hazards of indoor air pollution including low birth weight and its prevention.
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
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