High maternal serum ferritin in early pregnancy and risk of spontaneous preterm birth

Abstract

Previous studies have reported inconsistent associations between maternal serum ferritin concentrations and risk of preterm birth. The aim of this study was to examine the association between iron biomarkers, including serum ferritin and risk of total, early and moderate-to-late spontaneous preterm birth (sPTB). This cohort study included women with singleton pregnancies who were attending first-trimester screening in New South Wales, Australia. sPTB births included births <37 weeks gestation following spontaneous labour or preterm premature rupture of the membranes (PPROM). Sera were analysed for iron: serum ferritin and sTfR; and inflammatory: C-reactive protein (CRP) biomarkers. Multivariate logistic regression evaluated the association between low and high iron levels and sPTB. Women with elevated serum ferritin concentrations were more likely to be older, nulliparous or have gestational diabetes. Multivariate analyses found increased odds of sPTB for women with elevated ferritin levels defined as >75th percentile (≥43 μg/L) (OR: 1.49, 95% CI: 1.06, 2.10) and >90th percentile (≥68 μg/L) (OR: 1.92, 95% CI: 1.25, 2.96). Increased odds of early and moderate-to late sPTB were associated with ferritin levels >90th (OR: 2.50, 95% CI: 1.32, 4.73) and >75th (OR: 1.56, 95% CI: 1.03, 2.37) percentiles, respectively. No association was found between sPTB, and elevated sTfR levels or iron deficiency. In conclusion, elevated early pregnancy maternal serum ferritin levels are associated with increased risk of sPTB from 34 weeks gestation. The usefulness of early pregnancy ferritin levels in identifying women at risk of sPTB warrants further investigation.