A prospective study of micronutrient status in adolescent pregnancy.

Background: Adolescents are more likely than adults to consume energy-dense, micronutrient-poor diets and to experience adverse pregnancy outcomes.

Objectives: The objectives were to assess micronutrient intake and blood biomarkers prospectively in pregnant adolescents recruited to the About Teenage Eating (ATE) Study and to determine associations with pregnancy outcome.

Design: Pregnant adolescents (n = 500) were recruited from 2 UK inner city populations. Dietary intake was assessed with three 24-h dietary recalls, and micronutrient status was assessed by measurement of third trimester blood biomarkers. Pregnancy outcomes included small-for-gestational age (SGA) birth and preterm delivery.

Results: Median iron and folate intakes were lower than UK and US recommended amounts. Folate and vitamin B-12 status were lower in smokers, despite no differences in dietary intake. Serum folate was <7.0 nmol/L in 12% of subjects, and serum total homocysteine (tHcy) was elevated (>10 micromol/L) in 20% of subjects. Fifty-two percent of the subjects had iron deficiency anemia, and 30% had serum 25-hydroxyvitamin D concentrations <25 nmol/L. The incidence of SGA birth was higher in subjects with poorer folate status (red blood cell folate, P = 0.003; serum folate, P = 0.02; tHcy, P = 0.01; simple regression) and those with low folate intakes, regardless of the inclusion (P = 0.021) or exclusion (P = 0.049) of intake from supplements (simple regression). Adjustment for confounding variables confirmed the independence of these associations. The risk of SGA birth was also higher in subjects with low food iron intake (P = 0.049), but not when intake included iron from supplements (P = 0.21). The risk of SGA birth was lower in subjects with iron deficiency anemia (P = 0.002).

Conclusion: Poor micronutrient intake and status increase the risk of SGA births in pregnant adolescents.