Maternal anemia and risk of adverse birth and health outcomes in low- and middle-income countries: systematic review and meta-analysis.

BACKGROUND Anemia is a leading cause of maternal deaths and adverse pregnancy outcomes in developing countries. OBJECTIVES We conducted a systematic review and meta-analysis to estimate the pooled prevalence of anemia, the association between maternal anemia and pregnancy outcomes, and the population-attributable fraction (PAF) of these outcomes that are due to anemia in low- and middle-income countries. DESIGN PubMed, EMBASE, CINAHL, and the British Nursing Index were searched from inception to May 2015 to identify cohort studies of the association between maternal anemia and pregnancy outcomes. The anemic group was defined as having hemoglobin concentrations <10 or <11 g/dL or hematocrit values <33% or <34% depending on the study. A metaregression and stratified analysis were performed to assess the effects of study and participant characteristics on adverse pregnancy risk. The pooled prevalence of anemia in pregnant women by region and country-income category was calculated with the use of a random-effects meta-analysis. RESULTS Of 8182 articles reviewed, 29 studies were included in the systematic review, and 26 studies were included in the meta-analysis. Overall, 42.7% (95% CI: 37.0%, 48.4%) of women experienced anemia during pregnancy in low- and middle-income countries. There were significantly higher risks of low birth weight (RR: 1.31; 95% CI: 1.13, 1.51), preterm birth (RR: 1.63; 95% CI: 1.33, 2.01), perinatal mortality (RR: 1.51; 95% CI: 1.30, 1.76), and neonatal mortality (RR: 2.72; 95% CI: 1.19, 6.25) in pregnant women with anemia. South Asian, African, and low-income countries had a higher pooled anemia prevalence than did other Asian and upper-middle-income countries. Overall, in low- and middle-income countries, 12% of low birth weight, 19% of preterm births, and 18% of perinatal mortality were attributable to maternal anemia. The proportion of adverse pregnancy outcomes attributable to anemia was higher in low-income countries and in the South Asian region. CONCLUSION Maternal anemia remains a significant health problem in low- and middle-income countries.