was analyzed. Birth weight was standardized for gestational age (z-score) and a multivariate regression analysis was performed to determine the relation between z-score as dependent variable and BMI, GWG, maternal age, infant sex, parity, educational status, smoking, hemorrhage, hypertensive syndrome of pregnancy and gestational diabetes, as independent variables. Results: Mean preconceptional BMI was 25.7 ± 5.2 Kg. Mean GWG was 14.5 ± 7.1 Kg. BMI was positively correlated to birth weight zscore and was associated with LGA and cesarean section. GWG was also positively correlated to birth weight z-score. Pregestational BMI (0,08), GWG (0,04), infant sex (0,31) and hypertensive syndrome of pregnancy (−0.29) explained 13.2% of birth weight Z-score. Maternal age did not contribute to the model. Parity, educational status, smoking, hemorrhage and gestational diabetes, were not related to birth weight in this model. Conclusions: Birth weight was mainly determined by infant sex and pregestational BMI. In the population studied, pregestational BMI had a stronger influence than GWG. Overweight and obese women should be careful of their GWG, but should be even more attentive to weight before conception. This is important as it is the only modifiable factor. This data does not allow concluding a specific BMI or GWG to decrease perinatal mortality, since only the effect on weight birth was studied.
OP33.02The concomitant effects of estimated fetal weight and maternal BMI on Cesarean delivery in nulliparous patientsObjectives: Prior studies have demonstrated that the likelihood of Cesarean delivery correlates to increasing estimated fetal size on third trimester ultrasound. Other studies have shown maternal BMI to be a significant risk factor for Cesarean delivery. We sought to determine if there was a BMI cutoff at which estimated fetal weight did not contribute to overall risk of Cesarean. Methods: This was a retrospective cohort study of 368 nulliparas with third trimester ultrasounds. Chi square and regression analyses were performed. The adjusted odds risk of Cesarean delivery was calculated as it correlated with earliest measured maternal BMI and fetal weight percentiles. Results: Increasing estimated fetal weight percentile was associated with an increasing adjusted odds ratio of Cesarean delivery in all patients (P 0.03). Increasing BMI similarly correlated with increasing risk of Cesarean delivery in all patients (P < 0.001). (Figure 1) A post hoc analysis revealed that in patients with a BMI of 35 or greater, the risk of Cesarean delivery due to BMI alone was such that the added effect of fetal estimated weight did not significantly change the overall risk (P 0.729). Conclusions: At a BMI cutoff of 35 and higher, estimated fetal weight percentile in the third trimester does not give added information to likelihood of having successful vaginal delivery. Attention to both fetal and maternal factors may lead to improved patient counseling during delivery planning.Supporting information can be found in the online versi...
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