Prepregnancy Healthy Lifestyle and Adverse Pregnancy Outcomes

Abstract

Objective: To investigate the association of healthy lifestyle factors before pregnancy (body mass index [BMI] 18.5-24.9, nonsmoking, 150 min/wk or more of moderate-to-vigorous physical activity, healthy eating [top 40% of Dietary Approaches to Stop Hypertension score], no or low-to-moderate alcohol intake [less than 15 g/d], and use of multivitamins) with risk of adverse pregnancy outcomes.

Methods: We conducted a secondary analysis of prospectively collected data for women without chronic diseases who are participating in an ongoing cohort in the United States (the NHSII [Nurses' Health Study II]). Healthy lifestyle factors preceding pregnancy were prospectively assessed every 2-4 years from 1991 to 2009 with validated measures. Reproductive history was self-reported in 2001 and 2009. A composite outcome of adverse pregnancy outcomes that included miscarriage, ectopic pregnancy, gestational diabetes, gestational hypertension, preeclampsia, preterm birth, stillbirth, or low birth weight was assessed.

Results: Overall, 15,509 women with 27,135 pregnancies were included. The mean maternal age was 35.1±4.2 years. Approximately one in three pregnancies (n=9,702, 35.8%) was complicated by one or more adverse pregnancy outcomes. The combination of six low-risk factors was inversely associated with risk of adverse pregnancy outcomes in a dose-dependent manner ( P for trend <.001). Compared with women who had zero or one healthy lifestyle factor, those with six had a 37% lower risk of adverse pregnancy outcomes (relative risk 0.63, 95% CI 0.55-0.72), driven primarily by lower risks of gestational diabetes, gestational hypertension, and low birth weight. All prepregnancy healthy lifestyle factors, except avoiding harmful alcohol consumption and regular physical activity, were independently associated with lower risk of adverse pregnancy outcomes after mutual adjustment for each other. Healthy BMI, high-quality diet, and multivitamin supplementation showed the strongest inverse associations with adverse pregnancy outcomes. If the observed relationships were causal, 19% of adverse pregnancy outcomes could have been prevented by the adoption of all six healthy lifestyle factors (population attributable risk 19%, 95% CI 13-26%).

Conclusion: Prepregnancy healthy lifestyle is associated with a substantially lower risk of adverse pregnancy outcomes and could be an effective intervention for the prevention of adverse pregnancy outcomes.