Maternal Anemia and Pregnancy Outcomes: A Population-based Study

Anemia is a common disorder that affects about 40% of pregnancies worldwide and has been associated with adverse events in both the mother and infant. An increased risk of cesarean delivery, red blood cell transfusion, and death has been documented in anemic pregnant women. An increased risk of preterm birth, low birth weight, and retinopathy of prematurity has also been documented in infants of anemic mothers. Yet, study results have been inconsistent. The researchers of this study sought to describe the adverse outcomes of anemia on mothers during pregnancy and their infants. The researchers performed a retrospective analysis of live births in California from January 1, 2007, through December 31, 2012, using data from the California Preterm Birth Initiative at the University of California, San Francisco. Included in the study were women with singleton births between 22 and 42 weeks, whose infants did not have chromosomal abnormalities or structural birth defects that caused morbidity and mortality at birth or during the first year of life. Also excluded from the sample were infants with birth weights greater than 3 SDs of the mean for sex and gestational age. The study sample included 2,869,415 pregnant women. Of this sample, 284,780 (9.9%) were diagnosed with anemia. Anemic pregnant women were identified using the International Classification of Diseases, Ninth Revision code for anemia during pregnancy or in the delivery hospital discharge record. The study reported that anemic pregnant women were more likely to have hypertension, diabetes, or fibroids than nonanemic pregnant women (respectively, 10.7% vs 6.6%, 10.4% vs 8.9%, and 2.4% vs 1.3%). The risks of placental complications, including placental abruption, placental insufficiency, and placental infarction, were also higher among anemic pregnant women versus nonanemic pregnant women (adjusted relative risk [aRR], 1.3-1.9), as was chorioamnionitis (aRR, 1.9-2.0). Anemic pregnant women were also more likely to require blood transfusion, hysterectomy, admission to the intensive care unit, or an unplanned operation following pregnancy (aRR, 2.6-6.9). The authors also examined the impact on infants born to mothers with anemia during pregnancy. Infants born to anemic mothers weremore likely than those of nonanemicmothers to be large for gestational age (10.8% vs 9.4%) and to be delivered before 36 weeks of gestation (8.9% vs 6.5%). The study concluded that a diagnosis of anemia in pregnancy is associated with higher risks of obstetric complications for the mother and preterm birth for the infant.