Correlates of intake of folic acid-containing supplements among pregnant women.

Population-based control group from the National Birth Defects Prevention Study. Analyzed data from 2518 control mothers with estimated due dates Oct 1997 to Dec 2000. Maternal interviews conducted primarily by telephone in English or Spanish, on average 8.6 months after delivery. Controls were randomly selected from birth certificates (Iowa, Massachusetts, and New Jersey) or birth hospitals (Arizona, California, Georgia, New York, and Texas) to represent the population; live-born infants with major malformations were ineligible as controls. Data on folic acid-containing supplement intake during the 12 weeks before conception through delivery were collected; timing was categorized as periconceptional, early, late, or no intake. Multinomial logistic regression (PROC CATMOD) was used to identify correlates relative to periconceptional intake; analyses included 1948 women with continuous or no FA intake.

53% began FA supplements during the periconceptional period, 35% during early pregnancy, 8% during late pregnancy (total 96% took FA-containing supplements at some time around conception or during pregnancy). Among FA-containing supplement users, 94% reported daily intake; 97% used prenatal vitamin/mineral formulations; 84% continued FA through delivery. Correlates of nonpericonceptional or late intake included being nonwhite or a non–English speaker, younger age, lower education, and Spanish language; fertility treatments were associated with higher likelihood of periconceptional use. Beginning prenatal care in the second trimester or later and recognizing pregnancy after the first trimester increased the odds of late or no FA intake. Authors conclude that identifying these correlates can inform interventions to improve early-pregnancy FA intake, with implications for neural tube defect prevention.

Self-reported supplement intake may be misclassified; timing and frequency rely on recall; small number of women with no FA intake reduces precision; potential selection bias; findings may not generalize beyond NBDS control population.