Abnormal maternal body mass index and obstetric and neonatal outcome

Objective. The objective of this study is to examine the effects of abnormal maternal body mass index (BMI), either underweight or severe or morbid obesity (BMI > 35), on obstetrical and neonatal outcomes. Methods. A three-year period (2.007-2.009) observational retrospective study was carried out in Granada (Spain). Women were categorized by first ten weeks of pregnancy BMI, according to World Health Organization (WHO) into three groups: underweight (< 18.5), normal (20-24.9), and severe or morbid obese (> 35). Obstetrical and neonatal outcomes were evaluated using normal group as reference after suitable adjustments for confounding factors. Results. 3.016 patients out of 12.781 single births were included. Maternal BMI classified 168 women (5.5 %) as underweight, 2.597 (86.1%) as normal, and 251 (8.3%) as severe or morbidly obese. As compared to normal women, underweight women were younger, and class II or III obese showed higher parity and higher incidence of hypertension disorders and Diabetes Mellitus. After controlling for these confounders, underweight women showed increased adjusted risk of oligohydramnios and low birth weight babies, and severe or morbidly obese women had an increased adjusted risk of Streptococcus Group B colonization, induction of labour, elective and emergency cesarean section, fetal macrosomia, fetal acidosis at birth, and perinatal mortality. Conclusions. Severe or morbid obesity were associated with an increased risk of adverse perinatal outcome and mortality and should be managed as high-risk pregnancies.