Dietary Supplement Intake and Fecundability in a Singapore Preconception Cohort Study

Abstract

Subfertility is a global problem affecting millions worldwide, with declining total fertility rates. Preconception dietary supplementation may improve fecundability, but the magnitude of impact remains unclear. This prospective cohort study aimed to examine the association of preconception micronutrient supplements with fecundability, measured by time to pregnancy (TTP). The study was conducted at KK Women’s and Children’s Hospital, Singapore, between February 2015 and October 2017, on 908 women aged 18-45 years old, who were trying to conceive and were enrolled in the Singapore PREconception Study of long-Term maternal and child Outcomes (S-PRESTO). Baseline sociodemographic characteristics and supplement intake were collected through face-to-face interviews. The fecundability ratio (FR) was estimated using discrete-time proportional hazard modelling. Adjusting for potentially confounding variables, folic acid (FA) (FR 1.26, 95% confidence interval 1.03–1.56) and iodine (1.28, 1.00–1.65) supplement users had higher fecundability compared to non-users. Conversely, evening primrose oil supplement users had lower fecundability (0.56, 0.31–0.99) than non-users. In this study, preconception FA and iodine supplementation were associated with shortened TTP, while evening primrose oil use was associated with longer TTP. Nonetheless, the association between supplement use and the magnitude of fecundability changes will need to be further confirmed with well-designed randomised controlled trials.

Modifiable Risk Factor Score and Fecundability in a Preconception Cohort in Singapore

“…20,21 Similarly, alcohol intake and nonuse of folic acid supplements have been consistently associated with reduced fecundability. [14][15][16][17][34][35][36][37] Other micronutrient supplements were not included in the risk score due to the lack of evidence on their…”

“…In this study, we did not include passive smokers given that active smoking is known to be associated with reduced fecundability . Similarly, alcohol intake and nonuse of folic acid supplements have been consistently associated with reduced fecundability . Other micronutrient supplements were not included in the risk score due to the lack of evidence on their role in fecundability.…”

“… 20 , 21 Similarly, alcohol intake and nonuse of folic acid supplements have been consistently associated with reduced fecundability. 14 , 15 , 16 , 17 , 34 , 35 , 36 , 37 Other micronutrient supplements were not included in the risk score due to the lack of evidence on their role in fecundability. Although temporally nonmodifiable, planning to conceive at a younger age is an important modifiable decision, with both natural fertility and fertility treatment success declining with age.…”

“…The total number of drinks was calculated and classified as 1 or fewer standard drink per week or more than 1 standard drink per week . Participants were asked if they had consumed any pills, tonics, or tablets to supplement their diet in the past 3 months; we identified and classified those with supplements containing folic acid (single or multivitamin/mineral form) as users or nonusers of folic acid supplements . Age at recruitment was classified as younger than 32 years or 32 years or older, based on evidence that female fertility decreases substantially starting approximately at age 32 years …”

“…The risk score was generated based on previous evidence from the S-PRESTO cohort 12 , 17 , 19 and a priori published risk factors for reduced fecundability. 1 , 14 , 15 , 16 , 20 , 21 Participants received a 1-point score for each of the following: unhealthy BMI (<18.5 or ≥23), unhealthy diet (vegetable intake <2 servings per day), ever smoker status, alcohol intake of more than 1 standard drink per week, folic acid supplement nonuser, and 32 years or older.…”