Effects of pre-pregnancy BMI and gestational weight gain on pregnancy and neonatal outcomes in Poland

Overweight and obesity are significant public health concerns, affecting pregnant women and potentially leading to numerous complications for both maternal and neonatal health. The aim of this study is to estimate how pre-pregnancy overweight and obesity, as well as gestational weight gain, influence pregnancy outcomes and neonatal health in Poland. The study material consisted of data from 2878 women aged 16-46 years from hospitals in Warsaw and Krosno. The analysis included data on the course of singleton pregnancies and the biological condition of the newborns, correlated with pre-pregnancy Body Mass Index (BMI) and gestational weight gain (GWG), which were compared to the standards set by the Institute of Medicine (IOM). Factor that significantly influences pre-pregnancy BMI and GWG is the number of pregnancies. For first-born women pre-pregnancy BMI was significantly lower than that of women giving birth for the second, third and subsequent times (ANOVA p < 0.0001), at the same time, the increase in weight in this group was the greatest (ANOVA p < 0.0001). The study found that pre-pregnancy BMI correlates more strongly with the occurrence of gestational diabetes than GWG above IOM recommendations (regression: p < 0.0001, R = 0.112 vs. p < 0.0001, R = 0.104). Analogous correlations were observed for the incidence of gestational hypertension and termination of pregnancy by caesarean section. Birth weight and length are significantly affected by both pre-pregnancy BMI and GWG but the effect of weight change is stronger (birth weight - pre-pregnancy BMI regression p < 0.0001, R = 0.116; GWG p < 0.0001, R = 0.248; birth length - pre-pregnancy BMI regression p < 0.0001, R = 0.087; GWG p < 0.0001, R = 0.180). An analogous relationship was observed for the presence of macrosomia. For APGAR scores, an inverse relationship was observed; while GWG did not show a significant relationship with the first minute score, perinatal neonatal status was significantly related to the mother's pre-pregnancy BMI (regression p = 0.0006). Similarly, pre-pregnancy maternal BMI > 25 significantly increased the odds of perinatal injury and breastfeeding difficulties.