Parental preconception BMI and infant birthweight
Figure 1 presents model estimates for parental BMI associations with
infant birthweight. There was weak evidence for an interaction between
parental BMIs for median birth weight (β=-0.98; 95%CI=[-1.90,
-0.05], p=0.04) with infants having increasing birth weight with
increasing parental BMI, when one parent has normal weight (Figures 1A
and 1C). When either parent was overweight or obese, although median
infant birthweight are higher (maternal β=15.9; 95%CI=[1.63, 30.1],
p=0.03 and paternal β=7.33; 95%CI=[0.297, 14.4] p=0.04), they were
not associated with increasing BMI of the other parent (Figure 1B and
Figure 1D).
Maternal overweight and obesity was associated with increased risk of
extreme LGA (95th percentile: β=-25.1; 95%CI=[5.07,
45.1], p=0.01), while there was no effect of increasing paternal BMI
(90th percentile: p=0.50; 95thpercentile: p=0.43). In both the median, 90th and
95th percentile models, there was no evidence of a
non-linear association between maternal BMI and birthweight (median:
p=0.61; 90th percentile: p=0.32;
95th percentile: p=0.70). However, in the
5th and 10th percentile regression
there was a strong non-linear association between maternal BMI and
infant birthweight (p=0.002 and p=0.03). Such that infant birthweight
increased with maternal BMI, approximately 27.5kg/m2or lower, but for maternal BMIs in the obese range
(>30kg/m2), the 5thpercentile of infant birthweight plateaued, indicating a greater
divergence from the median baby weights and greater risks of SGA. There
was no effect of paternal BMI and risk of SGA infants
(5th percentile: p=0.60; 10thpercentile: p=0.52).