Mild Thrombocytopenia and the Risk of Post-Partum Hemorrhage

Mild thrombocytopenia is common in pregnancy and considered benign. However, its association with postpartum hemorrhage (PPH) remains unclear, with emerging evidence suggesting a potential increase in bleeding risk.

To evaluate whether mild thrombocytopenia is independently associated with PPH risk.

We performed an electronic search using MEDLINE(R) with the OvidSP interface and PUBMED, Embase, Web of Science, Cochrane Library, and Clinicaltrials.gov up to April 8, 2025.

We included observational studies evaluating the association between mild thrombocytopenia and PPH.

Eight retrospective studies encompassing 79 126 women were included, of whom 9496 had mild thrombocytopenia. Mild thrombocytopenia was associated with increased risk of PPH (OR 1.68; 95% CI 1.25-2.26; I² = 89%). Women with mild thrombocytopenia had higher risks of blood transfusion (OR 1.47; 95% CI 1.11-1.97) and hemoglobin decline ≥ 3 g/dL (OR 1.56; 95% CI 1.03-2.36).

Mild thrombocytopenia was associated with an increased risk of PPH and related hemorrhagic outcomes in the available retrospective studies. Although these findings do not establish a causal relationship, they suggest that mild thrombocytopenia may represent a clinically relevant risk marker that could be considered during peripartum risk assessment. Prospective studies using standardized definitions of PPH are needed to confirm these findings. Study protocol can be assessed at PROSPERO International prospective register of systematic reviews (http://www.crd.york.ac.uk/PROSPERO, registration number CRD42025642731).