The relationship between maternal anemia during pregnancy with preterm birth: a systematic review and meta-analysis

Objective: Iron deficiency anemia is the most common cause of anemia during pregnancy. Other causes of anemia include parasitic diseases, micronutrient deficiencies, and genetic hemoglobin apathies. Maternal anemia during pregnancy is the most important public health problem. Since the relationship between maternal anemia by the months of pregnancy and premature birth has been reported differently in various studies; thus, this study aims to determine the relationship between maternal anemia during pregnancy and premature birth.Methods: This systematic review and meta-analysis article was designed based on the recommendations of PRISMA. This study was performed from 1990 to 2018. Articles extracted using related keywords such as maternal, anemia, premature birth, and pregnancy in databases, including Cochrane, Medline, Medlib, Web of Science, PubMed, Scopus, Springer, Science Direct, Embase, Google Scholar, Sid, Irandoc, Iranmedex, and Magiran. Relative risk and its confidence interval were extracted from each of the studies. The random effects model was used to combine study results and heterogeneity among the studies measured using I² index and the data were analyzed based by using STATA software version 3.2.Results: Overall 18 studies with sample sizes of 932 090 were entered into the meta-analysis. The overall relationship between maternal anemia during pregnancy and premature birth was significant (1.56 [95% CI: 1.25-1.95]). Maternal anemia in the first trimester increases the risk of premature birth (relative risk, 1.65 [95% CI: 1.31-2.08]). But, this relationship was not significant in the second (relative risk, 1.45 [95% CI: 0.79-2.65]) and third trimester (relative risk, 1.43 [95% CI: 0.82-2.51]).Conclusion: Maternal anemia during pregnancy can be considered as a risk factor for premature birth.