Association between maternal anemia at admission for delivery and adverse perinatal outcomes

Background: Maternal anemia is a risk factor for poor pregnancy outcomes and threatens maternal or fetal life. Anemia increases the risk of low birth weight and preterm birth. We aimed to determine the cutoff level of hemoglobin and risk factors for maternal anemia at admission for delivery and investigate the association between maternal anemia and adverse perinatal outcomes in contemporary Taiwanese women. Methods: About 32,234 women admitted to the Taipei Chang Gung Memorial Hospital from 2001 to 2016 were enrolled in this retrospective observational cohort study. The prevalence of pre-delivery maternal anemia in Taiwan and the maternal demographic and perinatal outcomes associated with maternal anemia was assessed. Results: The 10th and 5th percentile hemoglobin levels of the test cohort (2001-2008, n = 15,602) were 10.8 g/dL and 9.9 g/dL, respectively. In the study cohort (2009-2016, n = 13,026), women who were multiparous, who were aged >34 years, with history of cesarean delivery, and with history of uterine fibroids had higher prevalence of anemia. Anemic women were at increased risk of cesarean delivery, primary cesarean delivery, premature rupture of membranes, early preterm birth <34 weeks, having very low birth weight infants (<1,500 g), having large for gestational age infants, and neonatal intensive care center transfer, but at lower risk of having small for gestational age infants. Conclusion: Maternal anemia at delivery is a risk factor for primary cesarean delivery and adverse maternal and neonatal outcomes. Furthermore, we hypothesize that maternal anemia might increase fetoplacental vasculogenesis and angiogenesis as an adaptive response.