title: Maternal anemia and risk of adverse birth and health outcomes in low- and middle-income countries: systematic review and meta-analysis.
abstract: BACKGROUND
  Anemia is a leading cause of maternal deaths and adverse pregnancy outcomes in developing countries.
  
  
  OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  Maternal anemia remains a significant health problem in low- and middle-income countries.
authors.affiliation: Department of Global Health Policy, The University of Tokyo, Tokyo, Japan; Department of Population Science and Human Resource Development, University of Rajshahi, Rajshahi, Bangladesh; and mizanur_rub@yahoo.com.
authors.forename: Md Mizanur
authors.initials: MM
authors.lastname: Rahman
authors.affiliation: Department of Global Health Policy, The University of Tokyo, Tokyo, Japan;
authors.forename: Sarah Krull
authors.initials: SK
authors.lastname: Abe
authors.affiliation: Department of Global Health Policy, The University of Tokyo, Tokyo, Japan;
authors.forename: Md Shafiur
authors.initials: MS
authors.lastname: Rahman
authors.affiliation: Department of Global Health Policy, The University of Tokyo, Tokyo, Japan;
authors.forename: Mikiko
authors.initials: M
authors.lastname: Kanda
authors.affiliation: Department of Global Health Policy, The University of Tokyo, Tokyo, Japan;
authors.forename: Saki
authors.initials: S
authors.lastname: Narita
authors.affiliation: Department of Global Health Policy, The University of Tokyo, Tokyo, Japan;
authors.forename: Ver
authors.initials: V
authors.lastname: Bilano
authors.affiliation: Department of Health Policy, National Centre for Child Health and Development, Tokyo, Japan.
authors.forename: Erika
authors.initials: E
authors.lastname: Ota
authors.affiliation: Department of Global Health Policy, The University of Tokyo, Tokyo, Japan;
authors.forename: Stuart
authors.initials: S
authors.lastname: Gilmour
authors.affiliation: Department of Global Health Policy, The University of Tokyo, Tokyo, Japan;
authors.forename: Kenji
authors.initials: K
authors.lastname: Shibuya
mesh_terms: D000328:Adult; D000740:Anemia / Q000453:epidemiology / Q000503:physiopathology*; D018798:Anemia, Iron-Deficiency / Q000453:epidemiology / Q000503:physiopathology; D001361:Avitaminosis / Q000453:epidemiology / Q000503:physiopathology; D003906:Developing Countries; D005260:Female; D005317:Fetal Growth Retardation / Q000453:epidemiology / Q000209:etiology*; D005494:Folic Acid Deficiency / Q000453:epidemiology / Q000503:physiopathology; D006801:Humans; D007223:Infant; D007226:Infant Mortality; D007231:Infant, Newborn; D008297:Male; D039382:Maternal Nutritional Physiological Phenomena; D054238:Perinatal Mortality; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology / Q000503:physiopathology*; D047928:Premature Birth / Q000453:epidemiology / Q000209:etiology*; D015995:Prevalence; D012307:Risk Factors
keywords: birth and health outcomes; low- and middle-income countries; maternal anemia; meta-analysis; population-attributable fraction