Folic acid supplementation and fecundability: a Danish prospective cohort study

• Published in: European journal of clinical nutrition Vol. 70; no. 1; pp. 66 - 71
• Main Authors: Cueto, H T, Riis, A H, Hatch, E E, Wise, L A, Rothman, K J, Sørensen, H T, Mikkelsen, E M
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.01.2016; Nature Publishing Group
• Subjects: 692/308/174; 692/700/2814; Adult; Analysis; Clinical Nutrition; Denmark; Dietary Supplements; Epidemiology; Female; Fertility; Fertility - drug effects; Folic acid; Folic Acid - pharmacology; Humans; Internal Medicine; Medicine; Medicine & Public Health; Menstrual Cycle; Metabolic Diseases; Nutrition research; original-article; Physiological aspects; Pregnancy; Pregnancy Rate; Prospective Studies; Public Health; Reproduction - drug effects; Risk reduction; Vitamin B; Vitamins - pharmacology; Denmark
• ISSN: 0954-3007; 1476-5640
• DOI: 10.1038/ejcn.2015.94

Background/Objectives: Periconceptional folic acid (FA) supplementation reduces the risk of neural tube defects and has been associated with ovulatory function. However, only two studies have associated supplementation with multivitamins (MVs) that contained FA with increased pregnancy rates. We aimed to examine the association between FA supplementation (obtained either through single FA tablets or through MVs) and fecundability. Subjects/Methods: A prospective cohort study of 3895 Danish women who were planning a pregnancy between 2007 and 2011. We estimated fecundability ratios (FRs) and 95% confidence intervals (CIs) in relation to FA supplementation (either through single FA tablets or MV) using a proportional probabilities regression model, with adjustment for potential socio-demographic, reproductive and lifestyle confounders. In stratified analyses, we also estimated FR with 95% CI in relation to FA supplementation for women with regular and irregular cycles, respectively, and for women with short (<27 days), medium (27–29 days) and long cycles (⩾30 days), respectively. Results: FA supplementation was associated with increased fecundability (FR=1.15, 95% CI=1.06–1.25), compared with non-use. The adjusted FRs for FA supplement use relative to non-use were 1.35 (95% CI=1.12–1.65) and 1.11 (95% CI=1.01–1.22) for women with irregular and regular cycles, respectively, and 1.36 (95% CI=0.95–1.95), 1.10 (95% CI=0.98–1.22) and 1.24 (95% CI=1.10–1.41) for women with short (<27 days), medium (27–29 days) and long cycles (⩾30 days), respectively. Conclusions: FA supplementation was associated with increased fecundability, and this association appeared to be stronger among women with irregular cycles and among women with either short or long cycle length.