Association between Maternal and Infant Screen-time with Child Growth and Development: A Longitudinal Study

Abstract

Background:

Sedentary screen-time is an early modifiable risk factor for obesity and poor child development.

Objectives:

To examine the relationship between maternal and infant screen-time with child growth and development.

Methods:

Pregnant women were recruited for a cohort study related to maternal and infant development. Screen-time was assessed in mothers during pregnancy, and subsequently in children at 3-months, 12-months, and 24-months of age. Child anthropometry was measured and nuclear magnetic resonance quantified child fat mass. Fat mass index (FMI) was calculated. The Bayley Scales of Infant Development-III were used to assess child development. Linear regression models were used to assess the relationship between screen-time and child growth and development adjusted for covariates and stratified by sex.

Results:

Mother/child dyads (n=89) were mainly white (92.1%), and half were boys (52%). Both sexes increased screen-time between 12-months and 24-months (ps<0.05). Child screen-time was positively associated with FMI and negatively associated with development scores. In adjusted models, screen-time was positively associated with FMI in boys and meeting the screen-time guideline was associated with lower FMI in girls.

Conclusion:

Greater infant screen-time was related to higher adiposity. Though few relationships emerged, a cautionary approach to screen-time early in life may benefit child health.

INTRODUCTION

Excess weight in early childhood is a public health concern, as children who have overweight or obesity prior to kindergarten (5 years of age) are four times more likely to have obesity in adolescence.¹ Sedentary screen-time is a modifiable risk factor for obesity.^2,3 Recognizing the importance of screen-time and child movement throughout the day, the World Health Organization (WHO) recently released 24-Hour Movement guidelines describing adequate physical activity, sedentary time, and sleep for children.^4,5 Specific to sedentary time, these guidelines stipulate no sedentary screen-time in infants and toddlers (below 2 years of age) and limit to ≤1.0 hour/day for preschoolers (2–5 years),⁵ which aligns with similar guidelines from the American Academy of Pediatrics released on 2016.⁶ Some report inconsistent findings between screen-time and obesity in infants and toddlers,^7,8 possibly due to the short amount of time for excess weight to accumulate, and the adiposity rebound (change in weight-to-height ratio) which occurs during the preschool years. Beyond excess weight gain, screen-time may also negatively influence obtaining adequate sleep,⁹ cognitive development and behavioral problems,^10,11 as well as motor development.¹²

Despite the importance of reducing screen-time in early life, reports within the United States find many young children exceed the screen-time guideline.^13,14 Many parents (76.6%) report their child is already viewing screens daily before the age of 2 years (24-months of age),¹³ and most preschoolers (86%) exceed the ≤1.0 hour/day screen-time recommendation.¹⁴ Though screen-time is prevalent, a limitation of the current literature is few studies assess screen-time before 24 months of age or examine the trajectory of screen-time during infancy and toddlerhood. As demonstrated in a recent systematic review of screen-time in young children, few studies assessed screen-time before 6 months of age, and studies that did assess screen-time before 6 months of age were predominately cross-sectional.¹⁵ Child sex is an important consideration for screen-time as found in a recent longitudinal study that child screen-time was prospectively related to adiposity in preschool-age boys, but not girls.^16,17 Quantifying infant screen-time and describing trajectories of early infant screen-time in a longitudinal manner may help identify targets for early intervention and any sex specific considerations, thus reducing screen-time as children age.

Beyond examining the child’s own screen-time in infancy and toddlerhood, it is important to examine the maternal screen-time as an intervention target. It is well established that the mother’s own screen-time is related to their child’s screen-time,^18,19 even as early as pregnancy.²⁰ The mother’s own screen-time and screen-related parenting practices are common intervention targets to reduce child screen-time, mainly in preschoolers.²¹ These interventions focus on promoting active play and family physical activity, thus changing the social and physical environment of the home.²¹ However, the influence of the mother’s own screen-time on their child’s growth and development prior to the preschool years is unclear.

Considering the wide-spread use of screens by toddler age children, investigation into early origins of screen-time and its impact on growth and development is warranted. Further exploring trajectories in longitudinal study designs improves upon prior literature by identifying opportunities for intervention in mothers and children. Accordingly, the purpose of this study is to: 1) to describe child screen-time before 24-months, and 2) examine the relationship between maternal and infant screen-time with child growth and development.

METHODS

Participants

Pregnant women were recruited for a prospective cohort study related to maternal and infant development between 2011 and 2014 (GLOWING Study, NCT01131117).²² ​Flyers, in-person events at medical offices, health fairs, childcare centers, and other local venues were used for recruitment. To be included in the GLOWING study, mothers need to have a body mass index (BMI) between 18.5–35.0 kg/m² at the baseline visit, be in their second pregnancy, have a singleton pregnancy, be >21 years of age, and conceived the child without fertility treatments. Mothers were excluded at enrollment for various reasons, including preexisting medical conditions, medical complications, medications that may influence fetal growth during pregnancy, smoking, alcohol consumption, and above average physical activity (e.g., athletes). Infants were included in the study measurements from birth to 24-months of age if they were born at ≥37 weeks gestation but were excluded at any time point for medical conditions or use of medications related to child growth. The GLOWING Study was powered to detect a significant difference in infant weight-for-length percentile at 3-months between those born to mothers of normal and overweight (n=65/group, 130 total). To facilitate retention throughout the study, phone calls, letters, and email contacts were placed throughout the study until the child was 2-years of age.

The current report was conducted as a secondary analysis of a longitudinal study of pregnant women and their children. This report utilized maternal data during pregnancy and postpartum, along with data at postnatal ages of 3-, 12-, and 24-months, and following the STROBE Reporting guidelines for cohort studies (Supplementary Table 1). The University of Arkansas for Medical Sciences Institutional Review Board approved this study, and procedures were conducted in accordance with the Helsinki Declaration of 1975.

Procedure

At the baseline visit (4–10 weeks gestation), mothers provided written informed consent and completed demographic and health behavior questionnaires. Mothers received a low-intensity behavioral intervention, comprised of six educational sessions to encourage healthy gestational weight gain during pregnancy. Results of the intervention were compared to a historical control and are described elsewhere.^22,23 Height (cm) and weight (kg) was objectively measured to the nearest 0.1 unit by a trained researcher, and BMI was calculated. Maternal intelligence quotient (IQ) was assessed using the Wechsler Abbreviated Scale of Intelligence instrument at the 12-week visit,²⁴ a brief reliable measure of cognitive ability. At subsequent pregnancy visits (18, 24, and 30 weeks), the mother completed the same health behavior questionnaire, and was fitted with an accelerometer (Actical, Phillips Respironics Co Inc., Bend, Oregon, USA) on their ankle on the non-dominant side to wear for at least three days. Mothers and children returned for visits at 3-, 12-, and 24-months post-partum which included health questionnaires for the mother, and clinical assessments on the child to assess growth and development. At the 12- and 24-month visits, children wore an accelerometer on their ankle using a tight-fitting medical band for seven days continuously (24-hours/day).

Maternal and Infant Screen-time

Maternal screen-time was assessed during pregnancy (10, 18, and 30-weeks) and post-partum (3, 12, and 24-months). To assess habitual recreational screen-time, mothers were asked “how many hours per day did you watch television or videos or use the internet in the past week?” based on the National Health and Nutrition Examination Survey 2009–2010 questionnaire and comparable to other screen-time reports which are shown to be valid and reliable.²⁵ Like others,²⁵ response options included 0 hours, 1-hour, then increasing increments of 1-hour until 15-hours. Maternal screen-time responses were averaged across available time points for pregnancy and post-partum, and singular measurements were used if multiple time points were unavailable. Child screen-time was assessed at 3, 12 and 24-months of age. Mothers were asked “about how many hours per day did your child watch television or videos in the past week?”. Response options were the same as the maternal screen-time question. Child screen-time was classified by the WHO guideline of zero screen-time before 24-months, and ≤1hour/day of screen-time at 24-months.²⁶

Child Growth and Development

At the three post-partum visits, quantitative nuclear magnetic resonance (EchoMRI-AH small; Echo Medical Systems, Houston, Texas, USA) was conducted and used to quantify fat mass as previously described,²⁷ and anthropometry was objectively measured. Fat mass index (FMI) was calculated by dividing fat mass (kg) by infant length (m²).​ Bayley Scales of Infant Development – 3^rd edition (BSID-III) was administered at 3, 12 and 24-months of age to assess child development. The BSID- III assesses the following domains by direct assessment of the child: Cognitive; Language (expressive and receptive); and Motor skills (fine and gross motor). These domains were administered by licensed psychological examiners supervised by a licensed psychologist. BSID-III domain scores are reported using normative –referenced standard scores which have a mean of 100 (SD of 15) and a range from 40–160, with higher scores indicating higher mastery in the developmental skill evaluated.²⁸

Covariates

Maternal covariates for analysis included age at enrollment, race, early pregnancy BMI with weight from baseline visit (4–10 weeks), IQ, and sedentary time. Like screen-time, sedentary time was assessed at multiple time points and averaged for analysis, with singular time points used when multiple time points were unavailable. Sedentary time was defined as <100 counts/minute.²⁹ Mothers with complete sedentary time data for ≥3 days, including one weekend day were included in analysis. Child activity was expressed as counts per minute (CPM) of wear-time to assess overall level of activity. Non-wear was defined as any periods of >20 minutes of continuous zeroes was removed prior to analysis based upon previous literature.³⁰ Infants who wore the accelerometer for ≥2 days for ≥12 hours and included overnight sleep were included in analysis like other studies.³¹

Data Analysis

Maternal and child pairs with complete data for demographics, independent variables, dependent variables, and covariates were included in analysis. Results for both aims were stratified by sex due to early differences in growth and development, as found in a previous publication from this sample.³² For aim 1, which is to describe child screen-time before 24-months, central tendencies were calculated across time points (3-months, 12-months, and 24-months). Paired t-tests were used to compare differences in screen-time between time points (both 3 and 12 months, and 12 and 24 months) by sex. To examine differences in screen-time across time points, repeated measures Analysis of Variance was conducted to examine an interaction of screen-time and sex. For aim 2, which is to explore the relationship between maternal and infant screen-time with child growth and development, Pearson correlation coefficients were used to assess the relationship between independent variables (maternal and child screen-time) and dependent variables (child growth and development). Independent t-tests were used to compare differences in dependent variables between those who met and did not meet screen-time guidelines. Linear regression models were then used to assess the relationship between independent variables and dependent variables with adjustment for covariates.​ Maternal screen-time models were adjusted for maternal age at enrollment, race, IQ, early pregnancy BMI, and sedentary time during pregnancy. Child models were adjusted for maternal age at enrollment, race, IQ, early pregnancy BMI, and child CPM at that time point. A moderation analysis was conducted to explore the interaction of screen-time and sex on child growth and development with adjustment for the same covariates as the maternal and child models, respectively. Due to low compliance with the motor skills assessment, fewer participants were included in these models (n=86 at 12-months and n=67 in 24-months). All analyses were conducted in SAS 9.4 (Cary, N.C.), and significance was set at p<0.05 for main effects and p<0.10 for interaction terms.

RESULTS

In total, 255 mothers participated, with 176 providing complete measures at during pregnancy, 163 maternal-child dyads providing complete measures at 3-months, 122 providing complete data at 12-months, and 89 dyads providing complete data across all time points and available for analysis (Supplementary Figure 1). Included mothers had a slightly higher IQ (109.7±8.72) and were more likely to identify as white (92.2%) compared to mothers who were not included (IQ: 105.1±10.5, p=0.001; white: 70.4%, p=0.001). Children included in the analyses had a slightly lower FMI at 12-months (4.6±1.2 kg/m²), and higher language scores at 12-months (95.9±8.3) and cognitive scores at 24-months (99.5±9.9) compared to those not included (FMI: 5.1±1.5 kg/m²; p=0.02; language: 91.9±8.9, p=0.01; cognitive: 96.2±9.4, p=0.01). There were no other differences in independent variables, dependent variables, or covariates between those included and not included.

As shown in Table 1, included mother/child dyads watched screens for leisure for 3.9±2.2 hours/day in pregnancy and 3.5±2.0 hours/day during post-partum, and half of children were boys (52%). Boys were more active compared to girls at 24-months (p=0.001), and slightly more mothers of boys were classified as white than mothers of girls (p=0.05). Further, boys had slightly more activity and screen-time at 12-months (p=0.06 for both) than girls.

Table 1.

Descriptive characteristics of sample (n=89)^{^}

	Full Sample (n=89)			Boys (n=47)			Girls (n=42)			p-value
	Mean	SD	%	Mean	SD	%	Mean	SD	%
Maternal Characteristics
Age at enrollment (years)	29.9	3.6		29.8	3.9		30.1	3.3		0.71
Race										0.05
White			92.1			97.8			85.7
African American			6.7			2.2			11.9
Other			1.2			0			2.4
Pre-pregnancy body mass index (kg/m2)	25.7	4.2		25.8	4.3		25.4	4.2		0.88
Education
Partial College or less			25.9			27.6			23.8
College			49.4			46.8			52.4
Graduate Degree or higher			24.6			25.6			23.8
Intelligence Quotient	109.7	8.7		110.7	8.4		108.7	9.1		0.30
Sedentary time (minutes/day)	981.1	82.4		985.4	82.2		976.2	83.2		0.60
Pre-pregnancy screen-time (hours/day)	3.9	2.2		3.7	2.1		4.2	2.4		0.29
Postpartum screen-time (hours/day)	3.5	2.0		3.5	1.9		3.5	2.2		0.93
Child Screen-time
3-month screen-time (hours/day)	1.0	1.3		1.0	1.3		1.0	1.3		0.95
12-month screen-time (hours/day)	1.1	1.2		1.3	1.2		0.8	1.1		0.06
24-month screen-time (hours/day)	1.7	1.0		1.8	1.1		1.7	1.0		0.83
Child Growth and Development at 12-months
Physical Activity (counts per minute/day)%	385.9	142.0		414.2	159.6		353.6	112.5		0.06
Fat Mass Index (kg/m2)	4.6	1.2		4.4	0.9		4.8	1.4		0.17
Cognitive Score (range 40–160)	106.9	11.3		107.2	12.5		106.5	9.9		0.77
Language Score (range 40–160)	95.9	8.4		95.2	8.0		96.7	8.8		0.40
Motor Score (range 40–160)#	101.9	12.2		102.0	12.9		101.9	11.3		0.95
Child Growth and Development at 24-months
Physical Activity (counts per minute/day)a	728.8	210.8		808.5	222.3		643.3	160.4		0.001*
Fat Mass Index (kg/m2)	4.3	1.4		4.2	1.4		4.5	1.5		0.41
Cognitive Score (range 40–160)	99.5	9.9		100.5	11.8		98.4	7.4		0.31
Language Score (range 40–160)	99.7	9.9		99.7	11.5		99.8	7.8		0.94
Motor Score (range 40–160)b	102.4	10.8		101.3	11.2		103.6	10.5		0.38

^{^}Differences between boys and girls assessed using chi-square analysis and independent t-tests,

^*p<0.05;

^%73 included due to missing data;

^#only 86 included due to missing data;

^aincludes 79 due to missing data,

^bincludes 67 due to missing data

Aim 1: Describe child screen-time before 24-months

There was a significant increase in screen-time in both boys (0.42±1.3 hours/day, p=0.03) and girls (0.85±1.2 hours/day, p=0.001) between 12-months and 24-months. These estimates translate into an average of an additional 25.2 minutes for boys, and 50.4 minutes for girls. There was no interaction between screen-time and sex over time (p=0.30). As for guidelines, fewer boys met the guideline of no screen-viewing at 12-months (n=10, 21%) compared to girls (n=19, 45%, p=0.02).

Overall, about half (49% and 32%) of children met the WHO screen-time guideline of no screen-viewing at 3-months and 12-months, respectively. Around half (49%) met the WHO screen-time guideline of ≤1 hour/day at 24-months. There were no differences in meeting the screen-time guideline at 3-months (p=0.99) or 24-months (p=0.54) between sexes.

Aim 2: Screen-time, growth, and development

In unadjusted models, screen-time hours at 12-months were positively associated with FMI at 12-months (r=0.43) and 24-months (r=0.29, ps<0.05) in boys. Further, screen-time hours at 3-months were negatively associated with language score (r=−0.25, p=0.08) in boys. For girls, screen-time hours at 3-months were negatively associated with motor skills at 12-months (r=−0.33, p=0.03) and cognitive score at 24-months (r=−0.29, p=0.06).

When comparing those who met and those who did not meet screen-time guidelines, boys who met the screen-time guideline at 12-months (no screen-time) had a significantly lower FMI at 24-months (n=10, 3.3±0.8) compared to those who did not meet the screen-time guideline at 12-months (any screen-time, FMI: 4.5±1.4, p=0.001, Figure 1A.). In girls, those who met the screen-time guideline at 3-months (n=20) had a higher cognitive score at 24-months compared to those who did not meet the screen-time guideline (n=22, p=0.05, Figure 1B). There were no other significant associations between maternal or infant screen-time with child growth or development in unadjusted correlations (ps>0.05).

Figure 1. Differences in growth and development by meeting screen-time guideline.

Panel A. Fat Mass Index at 24-months in boy^

Panel B. Cognitive Score at 24-months in girl^

^Differences compared using an independent t-test, p<0.05*

In moderation analysis with adjustment for covariates, there was a significant interaction between sex and screen-time at 12-months with FMI at 12-months (p=0.01) and FMI at 24-months (p=0.01). No other significant interactions between sex and screen-time were found (p>0.10). After stratifying by sex, additional hours of screen-time at 12-months were related to a higher FMI at 12-months (β=0.43, SE=0.11, p=0.008) in boys (Supplementary Table 2). The association between screen-time at 12-months and FMI at 24-months was attenuated to non-significance in adjusted models in boys (p=0.06). In girls, every additional hour of screen-time in pregnancy was related to 2.28±0.69 lower motor skills score at 12-months (p=0.02, n=39). Screen-time at 3-months was not related to motor skills score at 12-months in adjusted models in girls (p=0.09).

As shown in Table 2, boys who met the screen-time guideline at 12-months had a significantly lower FMI score at 12-months compared to boys who did not meet the guideline (p=0.02). As for girls, meeting the screen-time guideline at 3-months was associated with a lower FMI at 24-months compared to those who did not meet the guideline (p=0.05). Unexpectedly, girls that met the screen-time guideline at 12-months had a lower motor skills score at 12-months compared to girls who did not meet the guideline (p=0.03).

Table 2.

Adjusted associations between maternal and child screen-time with child growth and developmental outcomes (n=89)

	Met Guideline (no screen-viewing) at 3-months			Met Guideline (no screen-viewing) at 12-months			Met Guideline (≤1 hour/day) at 24-months
	Beta	SE​	p-value​	Beta	SE​	p-value​	Beta	SE​	p-value​
Boys
12-months​
Fat Mass Index	0.16	0.38	0.67	−0.98	0.41	0.02*
Cognitive Score	−0.39	4.51	0.93	2.01	5.27	0.70
Language Score	0.11	2.87	0.96	3.67	3.30	0.27
Motor Skills score	3.83	4.74	0.42	3.51	5.60	0.53
24-months
Fat Mass Index	0.05	0.55	0.92	−1.07	0.58	0.07	0.28	0.51	0.57
Cognitive Score	2.53	4.08	0.54	−0.38	4.56	0.93	0.27	3.82	0.94
Language Score	1.87	3.43	0.58	−1.03	3.83	0.78	1.86	3.20	0.56
Motor Skills score	−1.71	4.44	0.70	−3.02	6.06	0.62	−0.98	4.51	0.82
Girls
12-months
Fat Mass Index	−0.72	0.38	0.06	0.11	0.41	0.78
Cognitive Score	−2.76	3.89	0.48	−6.35	3.78	0.10
Language Score	4.40	3.22	0.18	−3.20	3.32	0.34
Motor Skills score	7.70	4.55	0.10	−9.71	4.45	0.03*
24-months
Fat Mass Index	−1.01	0.51	0.05*	0.24	0.57	0.67	0.18	0.55	0.74
Cognitive Score	3.17	2.51	0.21	0.90	2.73	0.74	2.59	2.57	0.32
Language Score	−3.11	2.72	0.26	−1.81	2.94	0.54	1.94	2.80	0.49
Motor Skills score	−3.83	4.38	0.39	2.51	4.25	0.55	−2.24	3.99	0.57

Assessed using linear regression; Maternal models adjusted for maternal age at enrollment, race, IQ, pre-pregnancy BMI, and sedentary time during pregnancy. Child models adjusted for maternal age at enrollment, race, IQ, pre-pregnancy BMI, and child counts per minute at time point (12-months and 24-months respectively);

^*p<0.05

DISCUSSION

The purpose of this study was to describe child screen-time before 2 years of age and examine the relationship between maternal and child screen-time with child growth and development. In this sample, maternal and infant screen-time was related to higher child adiposity and lower motor skills in a sex dependent manner. Specifically, higher screen-time in boys was related a higher FMI, and meeting the screen-time guideline (no screen-viewing) in girls was associated with higher FMI. Importantly, this prospective cohort study provides evidence suggesting that reducing screen-time in early in life may be effective in improving child health and development.

In this study, screen-time increased in infants from 3-months to 24-months, between 12-months and 24-months of age. The increase in screen-time during infancy and toddlerhood aligns with other findings of increasing use from 12-months of age.¹³ Interestingly, others have found early screen-viewing patterns at 18-months of age to persist until the child enters school (5-years of age).³³ Another recent report amongst 411 infants found that infants at 6-months were only watching 34±3 minutes of screen-time/day,³⁴ which is much lower than the current cohort assessment of screen-time at 3-months of age. That paper assessed watching/looking at the TV, a cellphone or tablet which is slightly different to our current approach (TV and watching videos), but still supports that screen-time begins well before 24-months. The increase in screen-time between 12-months to 24-months of age is unexpected. Potential explanations for this increase include the child’s growing mobility, advancing verbal skills to communicate their screen-viewing preference, or the parent may use the TV to distract an active toddler. Considering the current sample was second-born children, this may be a time when the child begins to join in screen-time with their sibling or other family member.³⁵ Additional investigation into factors that drive increased screen-time between 12- and 24-months of age is warranted to reduce screen-time and allow children to exit toddlerhood near the guideline of ≤1 hour/day at 24-months.

Overall, there were few relationships between screen-time and adiposity in this sample. These results may be expected as a recent systematic review found an inconsistent relationship between infant screen-time and adiposity.⁷ Indeed, the association between screen-time and FMI in boys in this sample suggests that screen-time may have promoted obesogenic behaviors early in life, such as additional sedentary time, disrupted or shorter sleep, or permissive parenting around screen-time and other health behaviors.³⁶ As with others, the relationship was found mainly in boys but not girls.^16,17 The exact mechanism is unclear, though it may be hypothesized that screen-time serves as a proxy for sedentary behavior for boys not girls, as girls engage in differing sedentary behaviors than boys such as quiet play.^16,17 Another explanation is short sleep which may influence adiposity development.⁷ Screen-time, especially at night, may impair children’s ability to sleep,^9,37 and lead to metabolic consequences.³⁷ Though this relationship was only found in boys, lower screen-time early in life may provide benefit through less sleep disruption for many children.

The current study found evidence to target early child screen-time, but little for screen-time during pregnancy. Maternal preference for screen-time, and fewer social opportunities or environmental limitations at home to engage in gross or fine motor play have been proposed as potential factors that drive this relationship. A recent longitudinal cohort study of 70 children found that maternal moderate-to-vigorous physical activity, not sedentary time, was positively related to toddler motor skills (ages 12–30 months). Coupled with the current paper’s limited findings, it is still not clear if maternal level of activity may influence the programming of motor skills in utero.³⁸ As for maternal and family factors, less restrictions around screen-time may promote time spent in sedentary pursuits, thereby reducing opportunities to practice gross or fine motor skills.³⁹ This relationship between maternal screen-time and motor skills occurred in girls, not boys, which may be due to small sample size. Opportunities to support families and children to engage in healthy amounts of screen-time may translate into more opportunities to master motor skills.

Beyond the development of the WHO guidelines, sedentary screen-time has received renewed interest recently as social distancing guidelines for the COVID-19 pandemic forced many young children to stay home and required older children to engage in active screen-time for education purposes. Amidst changing guidance, disruptions in formal childcare, and limited opportunities for active play, parents reported higher screen-time for infants, toddlers,⁴⁰ and preschoolers compared to before the pandemic.^41,42 Indeed, children born during the pandemic have lower motor skills and developmental scores relative to children born before the pandemic.⁴³ These results may be due to a multitude of factors, such as limited socialization and activity, along with experiencing high levels of maternal stress during pregnancy and postpartum during this unprecedented time. Considering maternal stress and her own screen-time are related to higher child screen-time,^18,20 these results in combination with the current results of pregnancy screen-time underscore the importance of early intervention. The current results were collected prior to the pandemic but may suggest that there could be long-term consequences of early screen-time amongst children during the COVID-19 pandemic. Further investigation into the long-term impact of screen-time, maternal stress, child development, and consideration of other pandemic-related social environment changes is warranted to untangle the recent global pandemic.

The strengths of the current study include its longitudinal design, assessment of both maternal and child screen-time during a critical time in development, and objective measures of child growth and development. The limitations of the current study include the predominantly white sample, and sole assessment of TV and videos. This longitudinal study was focused on maternal and child growth, and pregnant women were excluded for various medical and behavioral reasons related to these metrics. The inclusion criteria may limit application of results to all mothers and children, including populations who consume alcohol and smoke during pregnancy, though this amount may be small.⁴⁴ Further, the included sample represents a third of those enrolled in this longitudinal study and may not represent those lost to follow up or not included in analysis. TV and videos are the most common forms of screen-time, and infants may not be subject to more advanced modalities (e.g., video games, desktop computers, laptops) prior to 24-months of age.⁴⁵ The screen-time questions in this study could be improved as they did not specifically query mobile device use which may provide additional screen-time. The questions were in 1-hour increments though querying in smaller intervals (e.g., 15 or 30 minutes) may provide more precise measures. Another consideration is that there are many comparisons made amongst this sample which may result in inflated type 1 error and significant findings due to chance. Stratification by sexes is important in early childhood but may also limit power of our analyses and the ability to account for other important factors. Another limitation is that there may be a reciprocal relationship between fat mass and motor development but was unable to be assessed in the current cohort.⁴⁶

The findings of the current study identify actionable items for future research. Complete elimination of screen-time prior to 24-months is likely not feasible but reducing below 60 minutes or further is advisable.^47,48 Though few relationships were found, a cautionary approach to screen-time early in life may still be warranted for future health benefit. The first steps include replication of these findings in diverse groups and consider sources of screen-time beyond the home. Early childhood education centers likely have regulations of no screen-time before 24-months,⁴⁹ but family childcare home settings may have differing regulations and practices.⁵⁰ Additional steps include exploration into the context and content of screen-time, including parental involvement, educational aspects, and any promotion of child movement. Ecological momentary assessment methods may be used to capture context and environment of screen-time in infancy, as they have been used to characterize toddler physical activity.⁵¹ The variability in context and content may contribute to the null results between screen-time and cognition and language as found by other studies.^52,53 Finally, multi-component interventions should be explored to reduce screen-time in infants and family members. A responsive parenting intervention found that intervening in the first pregnancy regarding feeding sleep, and active play was related to beneficial development for the first and second born child.⁵⁴

In this sample, infants were watching screens in their first months of life and continued to increase use through toddlerhood and preschool years. Screen-time early in life was related to child growth and development. Further exploration into the intricacies of screen-time, screen-time in different population groups, and early life interventions may build upon these findings. Considering the findings of this study and others, reducing screen-time in infancy may have benefits to a child’s development and long-term health.