Background. Maternal anemia is a ubiquitous pregnancy complication, and has been associated with an array of adverse perinatal and reproductive outcomes. Despite scores studies, the association between anemia and perinatal outcomes remains poorly understood. The objectives of our study were to describe the epidemiology of maternal anemia, and to examine the associations of maternal anemia with perinatal mortality and preterm birth.
Method. A prospective cohort study was conducted, using existing data from a population-based pregnancy-monitoring system in 13 counties in East China (1993–96). Women who delivered singleton infants at 20 to 44 weeks with at least one hemoglobin assessment during pregnancy were included (n=164,667). The prevalence of anemia (hemoglobin <10 g/dL) during pregnancy and rates of stillbirth, neonatal death, and preterm birth were estimated. Multivariable log-Binomial regression models were used to evaluate risk factors associated with anemia. Associations between anemia and adverse outcomes were examined using multiple Cox proportional hazards regression models after adjusting for a variety of confounding factors.
Results. The overall prevalence of anemia was 32.6%, with substantial variations across trimesters (11%, 20%, and 26% in the 1 st, 2nd and 3rd trimesters, respectively). Older maternal age, lower education, farm occupation, delayed prenatal care, pregnancy-induced hypertension and preeclampsia were associated with increased risk for anemia, whereas peri-conceptional folic acid use was associated with reduced risk for 1st trimester anemia. Anemia in the first half of pregnancy was associated with increased risk of stillbirth (adjusted hazard ratio (HR) 1.7, 95% confidence internal (CI) 1.1, 2.7), but not neonatal deaths. Anemia in the 1st trimester was associated with increased risk for preterm premature rupture of membranes (PROM). Women with hemoglobin ≤5 g/dL were at highest risk (HR 3.3, 95% CI 1.4, 7.7) with progressively declining risk with increasing hemoglobin levels. In contrast, anemia in the 3 rd trimester was associated with reduced risk for all preterm birth and spontaneous preterm labor, potentially due to hemo-dilution. Anemia was not associated with medically indicated preterm birth.
Conclusion. Anemia in early pregnancy was associated with increased risk for stillbirth and preterm PROM. These findings underscore that early identification and treatment to alleviate anemia may help improve adverse pregnancy outcomes and related complications.