Antioxidant vitamins, long-chain fatty acids, and spontaneous preterm birth

Neither macro- nor micronutrient supplements have been clearly demonstrated to reduce the risk of preterm birth. However, there has been little attention to carotenoids, tocopherols, and long-chain fatty acids other than n-3 polyunsaturates.

We conducted a case-control study nested in a large (n = 5337) prospective, multicenter cohort. All cohort women had an interview, examination, and venipuncture at 24-26 weeks' gestation. Frozen plasma samples in spontaneous preterm births (n = 207) and approximately 2-term controls per case (n = 443) were analyzed for carotenoids, retinol, tocopherols, and long-chain fatty acids. Fresh placentas were fixed, stained, and assessed (without knowledge of pregnancy outcome) for histologic evidence of infection or inflammation, decidual vasculopathy, and infarction.

High (above the median) plasma concentrations of alpha- and beta-carotene, alpha- and beta-cryptoxanthin, and lycopene were all associated with reductions in risk of spontaneous preterm birth, with evidence of dose-response effects across quartiles. Modest increases in risk were observed with elevated total monounsaturated, total polyunsaturated, and total n-6 polyunsaturated long-chain fatty acids concentrations. Paradoxically, a high gamma-tocopherol concentration was associated with increased preterm birth risk (adjusted odds ratio = 1.8 [95% confidence interval = 1.2-2.6]). Only one of the studied micronutrients (lutein) was independently associated with a reduced risk of decidual vasculopathy (0.5 [0.3-0.9]).

Carotenoids and long-chain fatty acids warrant further investigation in in vitro, animal, and human studies of preterm birth.