  the increasing prevalence of childhood obesity , especially in preschool aged children [ 1 , 2 ] , has stimulated research targeting critical periods of growth . according to freinkel 's hypothesis of  fuel - mediated teratogenesis , 
the intrauterine environment can influence changes in gene expression and affect the development and maturation of fetal organs and tissues [ 3 , 4 ] .
the postnatal period up to 2 years of age is also a critical period of growth . indeed ,
rapid infant weight gain is associated with an increased risk of obesity and metabolic consequences later in life [ 58 ] .  
these include metabolic parameters such as in utero glucose exposure [ 911 ] , maternal prepregnancy body mass index ( bmi ) [ 1214 ] , and maternal insulin sensitivity during pregnancy . in a cohort of low - income children , maternal obesity during pregnancy more than doubled the risk of obesity in children .
maternal diet and physical activity during pregnancy [ 1619 ] , as well as smoking may impact offspring risk of obesity and metabolic risk [ 2023 ] .
however , there is a paucity of literature examining these risk factors in very young children .   
in particular , breastfeeding has a protective role against the development of obesity [ 2427 ] .
harder et al . reported a dose - dependent association between breastfeeding and risk of obesity , where each month of prolonged breastfeeding decreased obesity risk in the child .
beyond the first few months of life , breast - fed infants gained less weight than formula - fed infants .
another study showed weight gain from 6 to 12 months was less in infants exclusively breastfed for 5 months compared to 2 months .
earlier introduction to complementary foods may also contribute to increased risk of childhood overweight [ 14 , 31 ] , however the evidence is inconsistent .
additionally , reduced physical activity and increased screen time ( television and video ) are associated with obesity risk in older children , although limited data is available in infants [ 33 , 34 ]
.    there is little known about the impact of maternal and infant lifestyle on weight gain and adiposity at 1 year of life .
the effect of screen time in infants on weight gain and adiposity has not been included as a potential factor in prior statistical models .
there is also little information on the effect of maternal physical activity on weight outcomes of offspring .
the objective of our study was to determine how maternal physical activity , maternal insulin sensitivity ( isogtt ) , prepregnancy bmi , infant feeding practices ( breastfeeding duration , age of introduction of formula , and complementary foods ) , and screen time contribute to infant weight gain and adiposity at 1 year of age .
the study protocol was approved by the research ethics board at mount sinai hospital and the hospital for sick children .
participants were recruited for this prospective cohort study at the time of antepartum gestational diabetes mellitus ( gdm ) screening and were consented to be followed into the postpartum .
all consenting women then completed a 3-h oral glucose tolerance test ( ogtt ) in late 2nd or early 3rd trimester .
venous blood samples were drawn at baseline , 60 , 120 , and 180  min after ingestion of a standard 100  g glucose load .
the pregnant women were then classified into 3 glucose tolerance groups : ( 1 ) gdm , as defined by the national diabetes data group ( nddg ) criteria ( requires at least two of the following : fasting glucose 5.8  mmol / l , 1  h postload glucose 10.6  mmol / l , 2  h postload glucose 9.2  mmol / l , or 3  h postload glucose 8.1  mmol / l ) ; ( 2 ) gestational impaired glucose tolerance ( gigt ) , defined as meeting only one of the above criteria ; ( 3 ) normal glucose tolerance ( ngt ) , defined as not meeting any of the nddg criteria .   
parental demographics , medical history and anthropometrics were collected during pregnancy at the time of the ogtt .
data collected included maternal age , maternal prepregnancy weight , maternal and paternal ethnicity , family history of diabetes , socioeconomic status , and maternal physical activity indices .
maternal isogtt was calculated from the ogtt using the matsuda index , which is well correlated with insulin sensitivity derived from the euglycemic - hyperglycemic clamp method .
physical activity was assessed using the baecke questionnaire , which has been validated in several populations including women of child - bearing age [ 37 , 38 ] .
the questionnaire was completed during the ogtt , with participants reporting on their physical activity in the year preceding the pregnancy .
the baecke questionnaire measures three domains of physical activity : ( i ) occupation - associated activity ( work index ) ; ( ii ) sport - related physical activity ( vigorous / sport index ) ; ( iii ) leisure - time physical activity not including sports ( leisure index ) .
the work index quantifies the exertion related to occupational activities , including sitting , standing , lifting , and walking , as well as effects on the individual ( e.g. , fatigue and perspiration ) .
the sport index characterizes vigorous / sport activity with respect to intensity ( using the updated compendium of physical activities ) .
these indices were calculated on a scale from 15 , where 5 represented the highest level of physical activity for each category .
for example , a score of 3 out of 5 for leisure index might indicate 
sometimes  walking or cycling for 1530  min and  seldom  watching television .
mean parental education score and occupation score was calculated on a scale of 17 and 19 , based on the hollingshead index , an established surrogate index of socioeconomic status . a maximum averaged parental score of 62 indicated the highest level of education and profession .  
infant information collected at birth included length of gestation , gender ( male or female ) , and birth weight .
at the 1 year visit , infant weight and length were measured , and weight - for - length z - score was calculated according to the world health organization ( who ) 2006 child growth standards   to provide a surrogate measure of adiposity . the infant lifestyle questionnaire was completed by the mothers when the infants were 3 and 12 months of age and provided information on exclusive breastfeeding duration , age of introduction to formula and cereal , and screen time based on predictors found to be important for the development of obesity ( average daily exposure to tv or video viewing , meals eaten while tv is on , tv in bedroom ) [ 34 , 42 ] .
infants born < 37 or > 42 weeks , twins , or those with medical illnesses that required prolonged hospitalization were excluded from the analysis .  
bivariate analysis of continuous variables with infant weight gain and weight - for - length z - score were assessed by spearman 's correlation analysis .
independent samples t - test or one - way analysis of variance ( anova ) and post hoc analysis ( fisher 's least significant difference ) were used to test differences in the outcome variables with maternal glucose tolerance group ( gdm , gigt , or ngt ) , gdm status ( yes / no ) , family history of diabetes ( yes / no ) , infant gender ( male / female ) , ethnicity ( caucasian or non - caucasian ) , age of introduction to formula ( at birth , 15 months , 6 months or never ) , and average daily screen time divided into 3 categories ( no screen time , < 60 minutes , and 60 minutes ) .
we converted age of introduction to formula into a categorical variable because although exclusive breastfeeding duration and age of introduction to formula are similar variables , they are not synonymous because some infants were never formula - fed ( n = 80 ) . variables determined to be significant from bivariate analyses , concurrently with variables known to influence infant weight gain and adiposity , were entered into multiple linear regression models .
two separate models were created for weight gain from birth to 1 year and weight - for - length z - score at 1 year .
nonmodifiable risk factors ( infant age , sex , ethnicity , birth weight , and family history of diabetes ) were forced into the model and modifiable risk factors ( maternal prepregnancy bmi , gdm status , maternal physical activity indices prior to pregnancy , socioeconomic status , maternal log isogtt , infant exclusive breastfeeding duration , age of introduction to formula , age of introduction to cereal , and daily screen time ) were entered according to the forward stepwise method .
descriptive characteristics and lifestyle measures are presented in table 1 for mothers and infants at 1-year postpartum ( n = 246 ) . from the time of consent
postnatally to the 1-year followup visit , 62 ( 20% ) of the original 311 infants were lost to followup .
there were no significant differences in gdm status , prepregnancy bmi , maternal education , or maternal physical activity between mothers retained in the study versus those lost to followup .
no significant differences were found for infant weight gain and weight - for - length z - score based on the mother 's gdm status ( yes / no ) or glucose tolerance group during pregnancy ( gdm , gigt , or ngt ) .
independent samples t - tests also showed no significant differences in the infant outcomes for family history of diabetes ( yes / no ) and infant ethnicity ( caucasian or non - caucasian ) .
males had greater weight gain than females ( p < 0.001 ) , however no differences between males and females for weight - for - length z - score were found ( p = 0.636 ) .
one - way anova showed significant differences in infant weight gain for age of formula introduction ( p = 0.001 ) and screen time ( p = 0.032 ) ( figure 1 ) .
similar trends for age of formula introduction were found for infant weight - for - length z - score at 1 year ( p = 0.012 ) . however no differences were found between 0 , < 60  min , or 60 minutes of daily screen time ( p = 0.19 ) .
spearman 's correlation analysis ( table 2 ) showed a negative association for infant weight gain with maternal pregravid vigorous / sport index ( p = 0.031 ) , exclusive breastfeeding duration ( p < 0.001 ) , and an earlier age of introduction to cereal ( p = 0.02 ) .
weight - for - length z - score was positively associated with maternal prepregnancy bmi ( p = 0.003 ) and birth weight ( p < 0.001 ) , and negatively associated with maternal log isogtt during pregnancy ( p = 0.031 ) and maternal pregravid vigorous / sport index ( p = 0.006 ) .
maternal pregravid vigorous / sport index was also positively correlated with isogtt during pregnancy ( p < 0.001 ) , as expected from previous data .
each month of prolonged exclusive breastfeeding reduced weight gain by 116.4  g , after adjustment for infant age , sex , infant ethnicity , family history of diabetes , and maternal pregravid vigorous / sport index ( p < 0.001 ) . after adjustment , each unit increase in maternal pregravid vigorous / sport index decreased weight gain by 218.6  g ( p = 0.016 ) . in total , 33% of the variance in the model for weight gain was explained by the sample .
infant birth weight , infant ethnicity , and family history of diabetes did not significantly predict infant weight gain at 1 year . additionally , socioeconomic status , maternal prepregnancy bmi , maternal isogtt , gdm status , maternal pregravid work index , maternal pregravid leisure index , infant age of introduction to formula , and infant screen time did not emerge in the model when entered . for weight - for - length z - score , an increase in one unit of maternal prepregnancy bmi ( kg / m )
was associated with an increase in weight - for - length z - score of 0.03 ( p = 0.016 ) , or one standard deviation change on the who child growth standards , after adjustment .
thus , mothers with a greater prepregnancy bmi were more likely to have heavier infants normalized for length .
in addition , each month of prolonged exclusive breastfeeding and unit increase in maternal pregravid vigorous / sport index decreased weight - for - length z - score by 0.08 ( p = 0.010 ) and 0.20 ( p = 0.031 ) , respectively .
infant sex , infant ethnicity , and family history of diabetes were not significantly associated with infant weight - for - length z - score .
variables that did not emerge in the model included : socioeconomic status , maternal isogtt , gdm status , maternal pregravid work index , maternal pregravid leisure index , infant age of introduction to formula , and infant screen time .
approximately , 19% of the variance in the model for weight - for - length z - score was explained by the sample .
  these findings demonstrate that maternal pregravid physical activity , prepregnancy bmi , and infant feeding practices have a significant influence on infant weight gain and adiposity .
weight gain from birth to 1 year was negatively predicted by infant female sex , maternal pregravid vigorous / sport activity , and exclusive breastfeeding duration and positively predicted by infant age at time of 1 year visit .
weight - for - length z - score at 1 year was negatively predicted by maternal pregravid vigorous / sport activity and exclusive breastfeeding duration and positively predicted by birth weight , infant age at time of 1 year visit , and maternal prepregnancy bmi .
factors that have been previously shown to influence infant weight gain and weight - for - length z - score , such as socioeconomic status or gdm status , were not significant in our model .
this may be due to the fact that women in this study tended to have excellent glycemic control , which was evidenced by normal birth weight in the gdm pregnancies .
the effect of maternal prepregnancy bmi on infant adiposity is consistent with existing literature [ 1214 , 31 ] . in mothers with ngt or gdm ,
maternal prepregnancy bmi was significantly associated with childhood overweight in both groups , even after adjustment for maternal glucose status and infant birth weight .
furthermore , knight and colleagues reported that the impact of maternal fasting plasma glucose in nondiabetic mothers on infant growth was transient , while maternal prepregnancy bmi and paternal bmi remained correlated with offspring bmi at 2 years of age .
thus , the authors suggested that parental obesity , shared environment , or genetic factors had a greater influence on childhood bmi than maternal fasting plasma glucose during pregnancy .  
after controlling for confounding factors , maternal pregravid vigorous / sport activity significantly predicted infant weight gain .
the mean pregravid vigorous / sport index in our study was 2.4 , which suggests that 1530  min of walking or cycling per day   in mothers prior to pregnancy may be beneficial for decreasing obesity risk of offspring .
maternal log isogtt did not predict infant growth at 1 year , after adjusting for maternal physical activity indices .
prior analyses by our group showed pregravid vigorous / sport activity was an independent predictor of maternal isogtt and reduced glucose intolerance in pregnancy .
taken together , pregravid physical activity may affect infant weight gain through a mechanism that partly involves maternal isogtt , however , these results suggest that maternal lifestyle may have a greater impact on infant weight gain than maternal glucose tolerance group or isogtt .
although daily screen time was not a significant predictor of infant weight gain or adiposity in our multivariate analyses , it was unsettling to find that more than half of the infants in our study were already exposed to television at 1 year of age and 11% of infants watched more than 2 hours of television per day .
infants with 60 minutes of screen time each day were heavier at 1 year of age than infants with 0 or < 60 minutes of daily screen time .
one possible explanation may include decreased overall activity levels in infants exposed to television for longer periods of time .
preschool children , more than 2 hours of television per day was associated with a higher risk of overweight and at risk for overweight and greater adiposity . despite the known effect of screen time on bmi in childhood [ 4547 ] ,
there is currently limited information on the effect of screen time under 2 years of age .   the mechanisms to explain the effects of breastfeeding compared to formula feeding may include different physiological and behavioural factors .
several studies [ 2427 ] , however not all [ 32 , 48 , 49 ] , suggest that breastfeeding has a protective role on later obesity risk .
after adjusting for confounding variables , infants exclusively breast fed for a longer duration had reduced weight gain and adiposity at 1 year .
this may be influenced by the unique metabolic factors in breast milk compared to formula , such as breast milk leptin [ 50 , 51 ] and adiponectin   that may induce earlier satiety .
the higher protein content of formula may also contribute to increased adiposity in formula fed infants .
koletzko and colleagues demonstrated that infants given formula with high protein content compared to infants given formula with low protein content resulted in increased weight at 2 years of age with no effect on infant length .
it is thought that the higher protein consumption results in higher insulin secretion and stimulates the expression of insulin - like growth factor i ( igf - i ) , leading to more adipogenic activity and adipocyte differentiation [ 54 , 55 ] .
additionally , behavioural differences between breast - fed and formula - fed infants may affect infant energy intake .
studies have shown that there is less maternal control and a greater response to the infant 's hunger and satiety cues with breastfeeding compared to formula feeding [ 56 , 57 ] .
there is also a lower frequency of meals and a higher uniformity of feeding volumes in formula - fed infants compared to breast - fed infants .  
although some studies have reported the timing of cereal introduction as a positive predictor of infant weight gain , it did not emerge in our multivariate analyses . in a recent study , huh and colleagues noted that the timing of the introduction of solid foods on the odds of obesity at 3 years of age varied by breastfeeding status .
infants that were introduced to solid foods before 4 months and were never breast fed or stopped breastfeeding before 4 months had a sixfold increase in the odds of obesity compared to infants breast fed for more than 4 months . since our study population was introduced to cereal later than 4 months ( 5.5  1.1 months )
altogether , our findings on infant feeding suggest that exclusive breastfeeding duration may be more predictive of infant weight gain and adiposity than age of formula or cereal introduction .  
this study should be viewed in context of certain strengths and limitations . due to the assessment of glucose tolerance in the late 2nd or 3rd trimester of pregnancy
, we can not completely exclude the possibility that some individuals may have received treatments following ogtt that could affect in utero glucose exposure and isogtt on infant outcomes .
although data was available on the type of intervention ( diet therapy or other ) , glycemic control during pregnancy could not be determined .
other limitations included the lack of data on maternal diet and maternal physical activity during pregnancy in our study .
proposed that maternal energy intake influenced energy intake in children more than intrauterine exposure to diabetes , which suggests maternal energy intake should be included in future studies .
additionally , our study population had a large proportion of caucasian infants and highly educated parents , and it is unclear whether results may be extended to other ethnic backgrounds or families with lower socioeconomic status .
loss to followup was 20% , and although there were no differences in maternal factors between those who left and remained in the study , feeding practices of the infants may have differed .
we were also unable to report on infant physical activity due to challenges in capturing physical activity accurately and objectively in infants .
nevertheless , we examined maternal and infant lifestyle variables that have not been previously studied together , providing further insight into the effects of the maternal and infant environment on weight gain and adiposity while controlling for important confounding variables .    in summary , increased maternal pregravid physical activity and longer exclusive breastfeeding duration may have a critical influence on reducing infant weight gain and adiposity as early as 1 year of age .
results from this study support the recommendation for exclusive breastfeeding in infancy , and suggest maternal physical activity may also influence postnatal outcomes .
future directions include examining the additive effects of maternal diet during and after pregnancy , infant physical activity , and sedentary time on infant weight gain and adiposity .
the evaluation of paternal physical activity may also provide insight into the impact of family lifestyle on infant growth .
longitudinal followup of these children will examine the effects of maternal and infant factors on bmi and adiposity in early childhood beyond 1 year of age .
 increasing evidence supports the contribution of intrauterine environmental exposures on obesity risk in offspring . 
 few studies have included maternal and infant lifestyle factors . 
 our objective was to study the impact of maternal physical activity , infant feeding , and screen time on offspring weight gain and adiposity . in a prospective cohort study , 
 246 mothers underwent testing during pregnancy to assess glucose tolerance status and insulin sensitivity . 
 anthropometry and questionnaires on physical activity , infant feeding , and screen time were completed . 
 multiple - linear regression was performed to examine the impact of maternal and infant factors on infant weight gain and weight - for - length z - score at 1 year . 
 infant weight outcomes were negatively predicted by maternal pregravid vigorous / sport index and exclusive breastfeeding duration . 
 after adjustment , each unit increase in maternal pregravid vigorous / sport index decreased infant weight gain by 218.6 g ( t = 2.44 , p = 0.016 ) and weight - for - length z - score by 0.20 ( t = 2.17 , p = 0.031 ) . 
 each month of exclusive breastfeeding reduced infant weight gain by 116.4  g ( t = 3.97 , p < 0.001 ) and weight - for - length z - score by 0.08 ( t = 2.59 , p = 0.01 ) . 
 maternal pregravid physical activity and exclusive breastfeeding duration are associated with weight gain and adiposity as early as 1 year of age . 
1. Introduction
2. Methods
3. Results
4. Discussion