Context Some evidence has shown an association between maternal vitamin B12 levels and the development of preeclampsia in pregnant women, but the relationship between preeclampsia and vitamin B12 is not clear. Objective The aim of this systematic review was to compare serum vitamin B12 levels in women with preeclampsia with those in normotensive pregnant women. Data Sources The PubMed/MEDLINE, Scopus, and Web of Science databases were searched up to August 2019, along with the reference lists of included articles. Study Selection The literature was searched for observational studies that investigated vitamin B12 levels in women with preeclampsia. Data Extraction Data were extracted independently by 2 authors. Data were pooled using a random-effects model. Results Vitamin B12 levels in women with preeclampsia were significantly lower than those in healthy women (mean, −15.24 pg/mL; 95%CI, −27.52 to −2.954; P < 0.015), but heterogeneity between studies was high (I2 = 97.8%; P = 0.0103). Subgroup analyses based on folic acid supplementation, homocysteine concentrations, and gestational age at the time of sampling for vitamin B12 assessment did not identify the sources of heterogeneity. Conclusions Women with preeclampsia had significantly lower vitamin B12 concentrations than normotensive pregnant women.

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