Mother's own birth weight influences the rate of small-for-gestational-age births: an analysis by maternal body mass index

Abstract

ObjectiveIndividuals with low birth weight, especially when small for gestational age (SGA), can have altered postnatal growth that may be due to metabolic reprogramming. Women born small due to SGA are also at risk for delivering an SGA infant themselves. This study tests the hypothesis that mother's own birth weight (BW) influences the rate of SGA births but that this effect is modified by maternal body mass index (BMI).Study designLiveborn singleton data from the National Maternal and Infant Health Survey including mother's BW and detailed pregnancy outcome information were used. The data were collected in 1988 using sampling techniques that allow extrapolation of findings to the general U.S. population by weighted analyses. Rates for SGA births (<10th centile for 1988 births) were stratified by mother's BW across BMI categories of <20 (underweight), 20-24.9 (normal), 25-29.9 (overweight), and ≥30 (obese) after adjusting for weighted sampling.ResultsOut of 6744 births in the sample, there were 1243 SGA infants. This corresponds to a weighted population sample of 2,972,894 births and an SGA rate of 9.1%. SGA rates stratified on mother's BW and BMI at delivery are presented in the Table.ConclusionLower maternal BW is associated with higher SGA rates for all BMI categories except for BW <1500 g, which likely reflects more preterm rather than SGA births. However, extremes of BMI (underweight and overweight) have the highest rates of SGA birth across almost all maternal BW strata. These data suggest the possibility that maternal BW effects on pregnancy outcomes such as SGA births may be dependent on the maternal metabolic status as reflected by BMI.Tabled 1SGA rates (per 100 live births) by maternal BW and BMIMaternalBMIBW (g)<2020-24.925-29.9≥30<150019.39.96.72.71500-249920.517.612.412.72500-299913.810.610.217.03000-349910.65.67.18.63500-39999.54.85.99.5≥40004.82.21.37.6 Open table in a new tab ObjectiveIndividuals with low birth weight, especially when small for gestational age (SGA), can have altered postnatal growth that may be due to metabolic reprogramming. Women born small due to SGA are also at risk for delivering an SGA infant themselves. This study tests the hypothesis that mother's own birth weight (BW) influences the rate of SGA births but that this effect is modified by maternal body mass index (BMI). Individuals with low birth weight, especially when small for gestational age (SGA), can have altered postnatal growth that may be due to metabolic reprogramming. Women born small due to SGA are also at risk for delivering an SGA infant themselves. This study tests the hypothesis that mother's own birth weight (BW) influences the rate of SGA births but that this effect is modified by maternal body mass index (BMI). Study designLiveborn singleton data from the National Maternal and Infant Health Survey including mother's BW and detailed pregnancy outcome information were used. The data were collected in 1988 using sampling techniques that allow extrapolation of findings to the general U.S. population by weighted analyses. Rates for SGA births (<10th centile for 1988 births) were stratified by mother's BW across BMI categories of <20 (underweight), 20-24.9 (normal), 25-29.9 (overweight), and ≥30 (obese) after adjusting for weighted sampling. Liveborn singleton data from the National Maternal and Infant Health Survey including mother's BW and detailed pregnancy outcome information were used. The data were collected in 1988 using sampling techniques that allow extrapolation of findings to the general U.S. population by weighted analyses. Rates for SGA births (<10th centile for 1988 births) were stratified by mother's BW across BMI categories of <20 (underweight), 20-24.9 (normal), 25-29.9 (overweight), and ≥30 (obese) after adjusting for weighted sampling. ResultsOut of 6744 births in the sample, there were 1243 SGA infants. This corresponds to a weighted population sample of 2,972,894 births and an SGA rate of 9.1%. SGA rates stratified on mother's BW and BMI at delivery are presented in the Table. Out of 6744 births in the sample, there were 1243 SGA infants. This corresponds to a weighted population sample of 2,972,894 births and an SGA rate of 9.1%. SGA rates stratified on mother's BW and BMI at delivery are presented in the Table. ConclusionLower maternal BW is associated with higher SGA rates for all BMI categories except for BW <1500 g, which likely reflects more preterm rather than SGA births. However, extremes of BMI (underweight and overweight) have the highest rates of SGA birth across almost all maternal BW strata. These data suggest the possibility that maternal BW effects on pregnancy outcomes such as SGA births may be dependent on the maternal metabolic status as reflected by BMI.Tabled 1SGA rates (per 100 live births) by maternal BW and BMIMaternalBMIBW (g)<2020-24.925-29.9≥30<150019.39.96.72.71500-249920.517.612.412.72500-299913.810.610.217.03000-349910.65.67.18.63500-39999.54.85.99.5≥40004.82.21.37.6 Open table in a new tab Lower maternal BW is associated with higher SGA rates for all BMI categories except for BW <1500 g, which likely reflects more preterm rather than SGA births. However, extremes of BMI (underweight and overweight) have the highest rates of SGA birth across almost all maternal BW strata. These data suggest the possibility that maternal BW effects on pregnancy outcomes such as SGA births may be dependent on the maternal metabolic status as reflected by BMI.Tabled 1SGA rates (per 100 live births) by maternal BW and BMIMaternalBMIBW (g)<2020-24.925-29.9≥30<150019.39.96.72.71500-249920.517.612.412.72500-299913.810.610.217.03000-349910.65.67.18.63500-39999.54.85.99.5≥40004.82.21.37.6 Open table in a new tab