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

Background: 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.

Methods: 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.

Results: 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]).

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