Folate intake and ovarian reserve among women attending a fertility center.

ObjectiveTo examine the association between dietary folate intake and antral follicle count (AFC) among women seeing treatment for infertility.DesignCohort study.SettingAcademic fertility center.PatientsA total of 552 women attending the Massachusetts General Hospital Fertility Center (2007-2019) who participated in the Environment and Reproductive Health Study.InterventionsNone. Folate intake was measured with a validated food frequency questionnaire at study entry. Multivariable Poisson regression models with robust standard errors were used to estimate the association of folate intake with AFC adjusting for calorie intake, age, body mass index, physical activity, education, smoking status, year of AFC, and intakes of vitamin B12, iron, and vitamin D. Nonlinearity was assessed with restricted cubic splines.Main outcome measureAFC as measured by transvaginal ultrasonography as part of routine care.ResultsAmong the 552 women (median age, 35.0 years; median folate intake, 1,005 μg/d), total and supplemental folate intake had a significant nonlinear relationship with AFC. There was a positive linear association with AFC up to approximately 1,200 μg/d for total folate intake and up to 800 μg/d for supplemental folate intake; however, there was no additional benefit of higher folate intakes. The magnitude of the association was modest; for example, the predicted adjusted difference in AFC between a woman consuming 400 vs. 800 μg/d of supplemental folate was approximately 1.5 follicles.ConclusionHigher intake of folate, particularly from supplements, was associated with modestly higher ovarian reserve as measured by AFC among women attending a fertility center.Clinical trial registration numberThis trial was registered at clinicaltrials.gov as NCT00011713.