Prenatal anemia and postpartum haemorrhage risk: A systematic review and
meta-analysis
Abstract
Background: Postpartum hemorrhage (PPH) is the leading cause of maternal
mortality, with loss of uterine tonicity as the main underlying cause.
While mechanistic studies suggest that anemia-induced hypoxia reduces
uterine tonicity, there is no meta-analysis of relevant clinical
studies. Objectives: To conduct a systematic review/meta-analysis
synthesizing clinical studies of the relationship between prenatal
anemia and PPH. Search Strategy: We used search terms combining
hemorrhage and anemia or their derivatives, and searched PUBMED/Medline,
EMBASE , Cochrane, PROSPERO and Web of Science. Selection Criteria:
Original peer-reviewed articles that measured an indicator of prenatal
anemia and postpartum hemorrhage or postpartum hemorrhage-related
mortality in humans. Data Collection and Analysis: Our primary analysis
used random effects models to synthesize odds-ratios extracted from the
studies. Heterogeneity was formally assessed with the Higgins’ I2
statistics and explored using meta-regression and subgroup analysis.
Main Results: Overall, anemia was not associated with PPH (OR: 1.39;
95% (CI): 0.64 – 3.01). There was no statistical association with mild
(OR=0.60; 95% CI: 0.31, 1.17, p-value = 0.13), or moderate anemia
(OR=2.09; 95% CI: 0.40, 11.1, p-value = 0.39) and the risk of PPH. Our
findings suggest that severe prenatal anemia increases postpartum
hemorrhage risk (OR=3.54; 95% CI: 1.20, 10.4, p-value = 0.02).
Conclusions: Mild and moderate prenatal anemia is not associated with
PPH risk. High quality prospective studies are critical to evaluating
the effect of severe anemia on PPH risk and related mortality. Funding:
None. Key words: Maternal anemia, Post-partum hemorrhage risk factors,
Post-partum hemorrhage-related mortality, Maternal mortality, Obstetric
Emergency.