The association of prepregnancy body mass index with pregnancy outcomes in triplet gestations.

The impact of obesity on triplet gestations is poorly understood. In this study, we investigate the association of obesity with birth outcomes in triplets. Triplet births in the state of Missouri from 1989 through 1997 were analyzed. Obesity was defined as maternal prepregnancy body mass index (BMI) >or=30 kg/m(2). We assessed the association between obesity and the following outcomes: stillbirth, preeclampsia, very preterm, small for gestational age (SGA), and a composite adverse birth outcome. We employed logistic regression with further correction for intracluster correlation to obtain adjusted estimates. A total of 667 triplet gestations were analyzed. As compared with normal-weight mothers, the likelihood of stillbirth and preeclampsia was higher among obese mothers (odds ratio[OR] = 3.70; 95% confidence interval [CI] = 1.37 to 9.97 and OR = 3.02; 95% CI = 1.69 to 5.40 respectively). Obese mothers were also about twice as likely to experience at least one of the adverse birth outcomes considered. Obese women with triplet gestations have about four- and threefold elevated risks for stillbirth and preeclampsia as compared with their counterparts with normal weight. This observation may be of utility in the preconceptional counseling of women considering the use of assisted reproductive technology.