Rankings of iron, vitamin D, and calcium intakes in relation to maternal characteristics of pregnant Canadian women

Iron, vitamin D, and calcium intakes in the prenatal period are important determinants of maternal and fetal health. The objective of this study was to examine iron, vitamin D, and calcium intakes from diet and supplements in relation to maternal characteristics. Data were collected in a subsample of 1186 pregnant women from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, a cohort study including pregnant women recruited from 10 Canadian sites between 2008 and 2011. A food frequency questionnaire was administered to obtain rankings of iron, calcium, and vitamin D intake (16-21 weeks of pregnancy). Intakes from supplements were obtained from a separate questionnaire (6-13 weeks of pregnancy). Women were divided into 2 groups according to the median total intake of each nutrient. Supplement intake was an important contributor to total iron intake (median 74%, interquartile range (IQR) 0%-81%) and total vitamin D intake (median 60%, IQR 0%-73%), while the opposite was observed for calcium (median 18%, IQR 0%-27%). Being born outside of Canada was significantly associated with lower total intakes of iron, vitamin D, and calcium (p <= 0.01 for all). Consistent positive indicators of supplement use (iron, vitamin D, and calcium) were maternal age over 30 years and holding a university degree. In conclusion, among Canadian women, the probability of having lower iron, vitamin D, and calcium intakes is higher among those born outside Canada; supplement intake is a major contributor to total iron and vitamin D intakes; and higher education level and age over 30 years are associated with supplement intake.