To determine vitamin D status and associated factors in a cohort of newly delivered infants and their mothers in Boston, Massachusetts.
Enrollment in this cross-sectional study took place from 2005 to 2007 in an urban Boston teaching hospital with 2500 births per year. A questionnaire and medical-record data were used to identify variables that are potentially associated with vitamin D deficiency (25-hydroxyvitamin D [25(OH)D] < 20 ng/mL). Infant and maternal blood was obtained by venipuncture within 72 hours of birth. The main outcome measure was infant and maternal 25(OH)D status, assessed by competitive protein binding.
We enrolled 459 healthy mother/infant pairs. After subsequent exclusions, analyses were performed on 376 newborns and 433 women. The median infant 25(OH)D level was 17.2 ng/mL (95% confidence interval [CI]: 16.0–18.8; range: <5.0 to 60.8 ng/mL). The median maternal 25(OH)D level was 24.8 ng/mL (95% CI: 23.2–25.8; range: <5.0 to 79.2 ng/mL). Overall, 58.0% of the infants and 35.8% of the mothers were vitamin D deficient (25[OH]D < 20 ng/mL); 38.0% of the infants and 23.1% of the mothers were severely deficient (25[OH]D < 15 ng/mL). Risk factors for infant vitamin D deficiency included maternal deficiency (adjusted odds ratio [aOR]: 5.28 [95% CI: 2.90–9.62]), winter birth (aOR: 3.86 [95% CI: 1.74–8.55]), black race (aOR: 3.36 [95% CI: 1.37–8.25]), and a maternal BMI of ≥35 (aOR: 2.78 [95% CI: 1.18–6.55]). Maternal prenatal-vitamin use throughout the second and third trimesters was protective against infant deficiency (aOR: 0.30 [95% CI: 0.16–0.56]). Similarly, prenatal-vitamin use of ≥5 times per week in the third trimester was protective for mothers (aOR: 0.37 [95% CI: 0.20–0.69]). Despite this, >30% of the women who took prenatal vitamins were still vitamin D deficient at the time of birth.
A high proportion of infants and their mothers in New England were vitamin D deficient. Prenatal vitamins may not contain enough vitamin D to ensure replete status at the time of birth.