Micronutrient supplementation during pregnancy and the risk of pregnancy-induced hypertension: A randomized clinical trial.

Background & Aims: Increasing evidence suggests that iron-containing multiple micronutrient may reduce the risk of pregnancy-induced hypertension including gestational hypertension or preeclampsia. We aimed to examine whether 30 mg iron plus folic acid or multiple micronutrients during pregnancy reduces the risk of pregnancy-induced hypertension.

Methods: We conducted a secondary data analysis by the dataset from a double-blind randomized controlled trial in China from 2006 to 2009 that was conducted to investigate the effects of multiple micronutrient supplements on adverse pregnancy outcomes when provided to pregnant women with no/mild anemia. We used logistic regression to estimate the adjusted odds ratio and 95% confidence interval and test for effect modification.

Results: The incidence of pregnancy-induced hypertension was 7.1% (423/5923), 6.3% (374/5933) and 6.3% (372/5914) among the pregnant women who took folic acid only, iron-folic acid and multiple micronutrient supplements, respectively. The adjusted odds ratios associated with iron-folic acid supplements and multiple micronutrient supplements for pregnancy-induced hypertension were both nearly 0.88 (95% confidence interval, 0.76-1.02), compared with folic acid supplements only. Among pregnant women aged 20-24 years, iron-folic acid (adjusted odds ratios: 0.81, 95% confidence interval: 0.67-0.96) or multiple micronutrient supplementation (adjusted odds ratios: 0.83, 95% confidence interval: 0.70-0.99) can significantly reduce the risk of pregnancy-induced hypertension compared to folic acid supplementation.

Conclusions: Overall, there were no significant differences in pregnancy-induced hypertension across supplement groups. However, among pregnant women aged 20-24 years, iron-containing multiple micronutrient supplementation was associated with a reduced risk of pregnancy-induced hypertension compared with folic acid supplements only.

Trial Registration: ClinicalTrials.gov NCT00133744.