The association between maternal obesity and fetomaternal outcomes in twin pregnancies.

The prevalence of overweight and obese people worldwide has dramatically increased in the last decades and is yet to peak. At the same time and partly due to obesity and associated assisted reproduction, twinning rates showed a clear rise in the last years. Adverse fetomaternal outcomes are known to occur in singleton and twin pregnancies in overweight and obese women. However, the impact of the obesity levels as defined by the World Health Organization on the outcomes of twin pregnancies has not been thoroughly studied. Therefore, the purpose of this study is to examine how maternal overweight, and the level of obesity affect fetomaternal outcomes in twin pregnancies, hypothesizing a higher likelihood for adverse outcomes with overweight and each obesity level. This is a retrospective cohort study with 2,349 twin pregnancies that delivered at the Buergerhospital Frankfurt, Germany between 2005 and 2020. The mothers were divided into exposure groups depending on their pre-gestational body mass index; these were normal weight (reference group), overweight and obesity levels I, II, and III. A multivariate logistic regression analysis was performed to assess the influence of overweight and obesity on gestational diabetes mellitus, preeclampsia, postpartum hemorrhage, intrauterine fetal death, and a five-minutes Apgar score below seven. The adjusted odds ratio for gestational diabetes compared to normal weight mothers were 1.47, 2.79, 4.05, and 6.40 for overweight and obesity levels I, II and III respectively (p = 0.015 for overweight and p < 0.001 for each obesity level). Maternal BMI had a significant association with the risk of preeclampsia (OR 1.04, p = 0.028). Overweight and obesity did not affect the odds of postpartum hemorrhage, fetal demise, or a low Apgar score. While maternal overweight and obesity did not influence the fetal outcomes in twin pregnancies, they significantly increased the risk of gestational diabetes and preeclampsia, and that risk is incremental with increasing level of obesity.