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Obstetrics & Gynecology:
doi: 10.1097/AOG.0b013e3182941d9a
Original Research

Maternal 25-Hydroxyvitamin D and Preterm Birth in Twin Gestations

Bodnar, Lisa M. PhD; Rouse, Dwight J. MD; Momirova, Valerija MS; Peaceman, Alan M. MD; Sciscione, Anthony DO; Spong, Catherine Y. MD; Varner, Michael W. MD; Malone, Fergal D. MD; Iams, Jay D. MD; Mercer, Brian M. MD; Thorp, John M. Jr MD; Sorokin, Yoram MD; Carpenter, Marshall W. MD; Lo, Julie MD; Ramin, Susan M. MD; Harper, Margaret MDMSc; for the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units (MFMU) Network

Supplemental Author Material
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Abstract

OBJECTIVE: To assess whether there was an independent association between maternal 25-hydroxyvitamin D concentrations at 24–28 weeks of gestation and preterm birth in a multicenter U.S. cohort of twin pregnancies.

METHODS: Serum samples from women who participated in a clinical trial of 17 α-hydroxyprogesterone caproate for the prevention of preterm birth in twin gestations (2004–2006) were assayed for 25-hydroxyvitamin D concentrations using liquid chromatography tandem mass spectrometry (n=211). Gestational age was determined early in pregnancy using a rigorous algorithm. Preterm birth was defined as delivery of the first twin or death of either twin at less than 35 weeks of gestation.

RESULTS: The mean serum 25-hydroxyvitamin D concentration was 82.7 nmol/L (standard deviation 31.5); 40.3% of women had concentrations less than 75 nmol/L. Preterm birth at less than 35 weeks of gestation occurred in 49.4% of women with 25-hydroxyvitamin D concentrations less than 75 nmol/L compared with 26.2% among those with concentrations of 75 nmol/L or more (P<.001). After adjustment for maternal race and ethnicity, study site, parity, prepregnancy body mass index, season, marital status, education, gestational age at blood sampling, smoking status, and 17 α-hydroxyprogesterone caproate treatment, maternal 25-hydroxyvitamin D concentration of 75 nmol/L or more was associated with a 60% reduction in the odds of preterm birth compared with concentrations less than 75 nmol/L (adjusted odds ratio [OR] 0.4, 95% confidence interval [CI] 0.2–0.8). A similar protective association was observed when studying preterm birth at less than 32 weeks of gestation (OR 0.2, 95% CI 0.1–0.6) and after confounder adjustment.

CONCLUSIONS: Late second-trimester maternal 25-hydroxyvitamin D concentrations less than 75 nmol/L are associated with an increase in the risk of preterm birth in this cohort of twin pregnancies.

LEVEL OF EVIDENCE: II

© 2013 by The American College of Obstetricians and Gynecologists.

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