Does The Available Evidence Support Guidelines for Pre-Pregnancy Weight Loss? A Scoping Review

Abstract

While the risks of being pregnant and giving birth in a higher BMI class (> 24.9 kg/m2) are well documented, the ways to mitigate this risk are not. Current recommendations suggest entering pregnancy at a “healthy” or “normal” weight, conventionally defined as having a BMI between 18.5-24.9 kg/m2. However, it is unreasonable to expect women whose BMI is significantly above 24.9 kg/m2 to lose enough weight to enter the “normal” BMI range before they conceive. Moreover, in the United States, 40% of women of childbearing age have a BMI > 30 kg/m2. A set of standard recommendations is needed as to how much weight such women should lose before conceiving, whether they should attempt to lose weight in the early months of pregnancy if they conceive unexpectedly, and how they should attempt this weight loss to support a healthy pregnancy and birth. This review explores whether such recommendations can be made using the available evidence on pre-pregnancy weight loss and outcomes of the incident pregnancy. We focus on exposure to preconception weight loss and weight loss attempts (i.e. via dietary restriction), evaluating studies that examine maternal and fetal health outcomes in women who experienced pre-pregnancy weight loss and/or dieting. We conclude that the evidence does not consistently support recommendations that women with BMI > 24.9 kg/m2 lose weight before becoming pregnant to reduce their risk for complications. Rather, we draw on alternative frameworks for care--including Health At Every Size (HAES), weight neutrality, and evidence concerning weight cycling and weight stigma--to advocate for a weight-neutral approach to pre-conception maternal health counseling.