The intergenerational effects on birth weight and its relations to maternal conditions, São Paulo, Brazil

Parents' birth weight acts as a predictor for the descendant birth weight, with the correlation more strongly transmitted through maternal line. The present research aims to study the correlation between the child's low or increased birth weight, the mother's birth weight, and maternal conditions.

773 mother-infant binomials were identified with information on both the baby's and the mother's birth weight recorded. Group studies were constituted, dividing the sample according to birth weight (<2,500 grams (g) and ≥3,500 grams (g)). The length at birth was also studied in children ≤47.5 cm (lower quartile). Chi(2) test or Fisher's exact test, Spearman's Rho, and odds ratio were performed in order to investigate the relation between the children's weight and length at birth and the mothers' and children's variables.

The girls were heavier at birth than their mothers, with an average increase at birth weight between the generations of 79 g. The child's birth weight <2,500 g did not show any correlation with maternal birth weight <2,500 g (Fisher 0.264; Spearman's Rho 0.048; OR 2.1 and OR lower 0.7) or with maternal stature below the lower quartile (<157 cm) (Chi (2) sig 0.323; with Spearman's Rho 0.036; OR 1.5 and OR lower 0.7). The child's low birth weight (<2,500 g) was lightly correlated with drug use by the mother during pregnancy (Fisher 0.083; Spearman's Rho 0.080; OR 4.9 and OR lower 1.0). The child's birth weight <2,500 g showed increased correlation with gestational age lower than 38 weeks and 3 days (Chi (2) sig 0.002; Spearman's Rho 0.113; OR 3.2 and OR lower 1.5). The child's weight at birth ≥3,500 g showed strong correlation with maternal weight at birth ≥3,500 g (Chi (2) sig 0; Spearman's Rho +0.142; OR 0.5 and OR upper 0.7). It was also revealed that the higher the maternal prepregnancy BMI, the stronger the correlation with child's birth weight ≥3,500 g ((maternal prepregnancy BMI > 25.0 with Chi (2) sig 0.013; Spearman's Rho 0.09; OR 1.54 and OR upper 2.17) and (maternal prepregnancy BMI > 30.0 with Chi (2) sig 0 Spearman's Rho 0.137; OR 2.58 and OR upper 4.26)). The child's length at birth in the lower quartile (≤47.5 cm) showed strong correlation with drug use by the mother during pregnancy (Chi (2) sig 0.004; Spearman's Rho 0.105; OR 4.3 and OR lower 1.5).

The mother's increased weight at birth and the prenatal overweight or obesity were correlated with increased weight and length at birth of the newborn, coupled with the tendency of increasing birth weight between generations of mothers and daughters. Also, descendants with smaller length at birth are the children of women with the lowest statures.