Mild gestational thrombocytopenia in primiparous women, does it affect risk of early postpartum hemorrhage? A retrospective cohort study.

Purpose: To assess whether women with mild gestational thrombocytopenia have a higher risk of postpartum hemorrhage.
Methods: A retrospective computerized database. Primiparous women that delivered at our center (2005-2019) were included; we excluded women with possible etiologies for thrombocytopenia such as systemic lupus or coagulation disorders, and hypertensive disorder of pregnancy. Demographics, obstetric characteristics, and maternal as well as neonatal data were compared between groups. The exposure measure of the study was mild thrombocytopenia (100,000-150,000) versus normal thrombocyte count (>150,000) at admission for labor. Postpartum hemorrhage (PPH) is defined as a clinical estimated blood loss of > 500 mL and/or a hemoglobin drop of ≥ 3 g/dl.
Results: Overall, 39,886 primiparous met the study's criteria, 5,209 (13.1%) had mild gestational thrombocytopenia (mean platelet count of 132.4 ± 13.2, study group) while 34,677 (86.9%) had normal platelet count at admission (mean of 221.6 ± 50.6, comparison group.) PPH occurred in 17.6% of the study group as opposed to 14% in the comparison group ( p  < .001). Similarly, all measures of increased bleeding were more common in the study group as compared to the comparison group, including rates of hemoglobin drop greater than 4 and 5 gram/dl, parenteral iron infusion, and blood products transfusion. On multivariable analysis, the aOR for PPH among women in the study group was 1.23 [1.11-1.36].
Conclusion: Primiparous women with mild gestational thrombocytopenia are at increased risk of peripartum hemorrhage, this should be considered a risk factor when assessing parturients' risk of PPH.