A systematic approach for establishing the range of recommended weight gain in pregnancy

Current approaches for establishing public health guidelines on the recommended range of weight gain in pregnancy are subjective and nonsystematic.

In this article, we outline how decision-making on gestational weight-gain guidelines could be aided by quantitative approaches used in noninferiority trials.

We reviewed the theoretical application of noninferiority margins to pregnancy weight-gain guidelines. A worked example illustrated the selection of the recommended range of pregnancy weight gain in women who delivered at the Magee-Womens Hospital, Pittsburgh, PA, in 2003-2010 by identifying weight-gain z scores in which risk of unplanned cesarean delivery, preterm birth, small-for-gestational-age infant, and large-for-gestational-age infant were not meaningfully increased (based on noninferiority margins of 10% and 20%).

In normal-weight women, lowest risk of adverse perinatal outcome was observed at a weight-gain z score of -0.2 SDs. With a noninferiority margin of 20%, risks of adverse outcome were not meaningfully increased from the -0.2-SD reference value between z scores of -0.97 and +0.33 SDs (which corresponded to 11.3-18.4 kg). In overweight women, the recommended range was much broader: -2.11 to +0.29 SDs (4.4-18.1 kg).

The new approach illustrated in this article has a number of advantages over current methods for establishing pregnancy weight-gain guidelines because it is systematic, it is reproducible, and it provides a tool for policy makers to derive guidelines that explicitly reflect values at which risk of adverse outcome becomes meaningfully increased.