Maternal Selenium Status During Early Gestation and Risk for Preterm Birth

Abstract

Preterm birth is a leading cause of perinatal mortality and morbidity with both short- and long-term adverse health outcomes for the child. Excessive inflammation (elevated immune response) increases the risk of premature rupture of the membranes and preterm birth. Low maternal serum levels of the trace metal selenium in early gestation are associated with inflammation and increase the risk of premature delivery. Low serum selenium levels have also been found in women with preeclampsia, a condition with a strong inflammatory component. Previous small studies investigating selenium plasma levels in mothers with term and preterm delivery suggest a role for low values in preterm birth, but the data were inconsistent. This prospective cohort study was designed to determine whether low maternal selenium serum levels in a large cohort of pregnant women followed up from early gestation to delivery are associated with preterm birth. The study was conducted over a period of 2 years in a population of 1197 Dutch women with singleton pregnancies who were followed up prospectively from 12 weeks of gestation to delivery. Women with known thyroid disease or type 1 diabetes were excluded from the study. Blood samples were drawn at 12 weeks' gestation for measurement of serum selenium. Births were either term or preterm deliveries; preterm births were categorized as either iatrogenic, spontaneous preterm labor with intact membranes, or as resulting from preterm premature rupture of the membranes. The incidence of preterm birth was 5.3% (n = 60); these 60 preterm deliveries included 21 with premature rupture of the membranes and 13 with preeclampsia. At 12 weeks of gestation, the serum selenium concentration was significantly lower among women who had a preterm birth (n = 60) compared with those who had term deliveries (n = 1069): the mean selenium serum concentration for preterm deliveries was 0.96 (standard deviation 0.14) μmol/L compared with term deliveries (1.02 [standard deviation 0.13] μmol/L; t = 2.9, P = 0.003). Women were grouped into 4 quartiles using serum selenium concentration at 12 weeks' gestation. The proportion of women with premature birth differed significantly by quartile (χ2 = 8.0, 3 degrees of freedom, P = 0.04). Univariate logistic regression analysis showed that the overall risk of preterm birth was twice as high among women in the lowest quartile of serum selenium at 12 weeks' gestation compared with those in the 3 higher quartiles. These results persisted after controlling for the occurrence of preeclampsia, the adjusted odds ratio was 2.18, with a 95% confidence interval of 1.25–3.77. These findings show that being in the lowest quartile of selenium concentration at 12 weeks' gestation is a significant independent risk factor for increased odds of preterm birth independent of having preeclampsia.