Folate Levels by Time Since Last Live Birth Among U.S. Women,2007–2016

Abstract

Background:

Folate depletion in the postpartum period may increase the risk of adverse pregnancy outcomes for women with a short interpregnancy interval following a live birth. We sought to examine folate levels by time since last live birth among U.S. women.

Materials and Methods:

Data were from 4,809 U.S. women, 20–44 years of age, participating in the National Health and Nutrition Examination Survey, 2007–2016. Red blood cell (RBC) folate was measured using microbiological assay on whole blood samples. Dietary folate intake and folic acid supplementation were measured during a 24-hour dietary recall. Prevalence of supplementation by time since last live birth was estimated from logistic regression models; mean levels of RBC folate and mean intake of dietary folate equivalent were estimated from linear regression models. Models were adjusted for maternal sociodemographic characteristics.

Results:

In adjusted models, supplementation (±standard error) was highest among women in the first year postpartum (31.7% ± 3.2) compared with nulliparous women (23.7% ± 1.9) and those 2–3 years (15.6% ± 1.9) and ≥3 years (18.4% ± 1.6) after last live birth. Mean RBC folate was highest among women in the first year postpartum, regardless of supplementation, with overall mean levels of 606 ± 15 ng/mL, compared with 484 ± 9, 477 ± 11, and 474 ± 7 among women in the aforementioned groups, respectively. Mean dietary folate intake was also highest among postpartum women: 542 ± 23 mcg/day, compared with 474 ± 12, 486 ± 21, and 467 ± 12.

Conclusions:

Folate levels are highest in the first year postpartum compared with other time periods within a woman's reproductive lifespan. These findings do not support the idea that postpartum U.S. women are depleted in folate, on average.