Effects of gestational weight gain and body mass index on obstetric outcome in Sweden.

OBJECTIVE: The objective of this study was to estimate the effects of low and high gestational weight gain, in different maternal Body Mass Index (BMI) classes, on obstetric and neonatal outcomes.
METHOD: A prospective population-based cohort study of 245,526 singleton term pregnancies. Women were grouped in five categories of BMI and in three gestational weight gain categories; < 8 kg (low weight gain), 8-16 kg and >16 kg (high weight gain). Obstetric and neonatal outcomes were evaluated after adjustments for maternal age, parity, smoking, year of birth. RESULT: Obese women with low gestational weight gain had a decreased risk for the following outcomes (adjusted odds ratio; 95% confidence interval): preeclampsia (0.52; 0.42-0.62), cesarean section (0.81; 0.73-0.90), instrumental delivery (0.75; 0.63-0.88), and LGA births (0.66; 0.59-0.75). There was a 2-fold increased risk for preeclampsia and LGA infants among average and overweight women with excessive weight gain. High gestational weight gain increased the risk for cesarean delivery in all maternal BMI classes.
CONCLUSION: The effects of high or low gestational weight gain differ depending on maternal BMI and the outcome variable studied. Obese women may benefit from a low weight gain during pregnancy.