Association of a Mediterranean Diet Pattern With Adverse Pregnancy Outcomes Among US Women

IMPORTANCE: The Mediterranean diet pattern is inversely associated with the leading causes of morbidity and mortality, including metabolic diseases and cardiovascular disease, but there are limited data on its association with adverse pregnancy outcomes (APOs) among US women. OBJECTIVE: To evaluate whether concordance to a Mediterranean diet pattern around the time of conception is associated with lower risk of developing any APO and individual APOs. DESIGN, SETTING, AND PARTICIPANTS: This prospective, multicenter, cohort study, the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be, enrolled 10 038 women between October 1, 2010, and September 30, 2013, with a final analytic sample of 7798 racially, ethnically, and geographically diverse women with singleton pregnancies who had complete diet data. Data analyses were completed between June 3, 2021, and April 7, 2022. EXPOSURES: An Alternate Mediterranean Diet (aMed) score (range, 0-9; low, 0-3; moderate, 4-5; and high, 6-9) was computed from data on habitual diet in the 3 months around conception, assessed using a semiquantitative food frequency questionnaire. MAIN OUTCOMES AND MEASURES: Adverse pregnancy outcomes were prospectively ascertained and defined as developing 1 or more of the following: preeclampsia or eclampsia, gestational hypertension, gestational diabetes, preterm birth, delivery of a small-for-gestational-age infant, or stillbirth. RESULTS: Of 7798 participants (mean [SD] age, 27.4 [5.5] years), 754 (9.7%) were aged 35 years or older, 816 (10.5%) were non-Hispanic Black, 1294 (16.6%) were Hispanic, and 1522 (19.5%) had obesity at baseline. The mean (SD) aMed score was 4.3 (2.1), and the prevalence of high, moderate, and low concordance to a Mediterranean diet pattern around the time of conception was 30.6% (n=2388), 31.2% (n=2430), and 38.2% (n=2980), respectively. In multivariable models, a high vs low aMed score was associated with 21% lower odds of any APO (adjusted odds ratio [aOR], 0.79 [95% CI, 0.68-0.92]), 28% lower odds of preeclampsia or eclampsia (aOR, 0.72 [95% CI, 0.55-0.93]), and 37% lower odds of gestational diabetes (aOR, 0.63 [95% CI, 0.44-0.90]). There were no differences by race, ethnicity, and prepregnancy body mass index, but associations were stronger among women aged 35 years or older (aOR, 0.54 [95% CI, 0.34-0.84]; P = .02 for interaction). When aMed score quintiles were evaluated, similar associations were observed, with higher scores being inversely associated with the incidence of any APO. CONCLUSIONS AND RELEVANCE: This cohort study suggests that greater adherence to a Mediterranean diet pattern is associated with lower risk of APOs, with evidence of a dose-response association. Intervention studies are needed to assess whether dietary modification around the time of conception can reduce risk of APOs and their downstream associations with future development of cardiovascular disease risk factors and overt disease.