Excessive weight gain in term twin pregnancies: examining the 2009 Institute of Medicine definitions

To estimate pregnancy outcomes in twin pregnancies with excessive weight gain, according to the 2009 Institute of Medicine (IOM) recommendations.

A retrospective cohort of 170 patients from a single practice with twin pregnancies at 37 weeks or more of gestation from 2005 to 2010 were analyzed. We compared outcomes between three cohorts based on the 2009 IOM recommendations for weight gain during pregnancy: poor weight gain, normal weight gain, and excessive weight gain. One-way analysis of variance and χ for trend were used when appropriate.

Comparing poor, normal, and excessive weight gain, the proportion of women delivering both newborns weighing more than 2,500 g increased from 40% to 60.5% to 79.5% across the three groups (P<.001). Additionally, the mean birth weight of the larger (P<.001) and smaller (P=.002) twin increased significantly across the three groups. The proportion of women with gestational diabetes, gestational hypertension, or pre-eclampsia did not increase significantly across the three subgroups. Our results were similar when we only included women with a normal prepregnancy body mass index.

Excessive weight gain in term twin gestations, as defined by the IOM, does not appear to be associated with worse maternal outcomes and is associated with larger birth weights. Our results call into question the 2009 IOM definition of excessive weight gain for a twin pregnancy.