Predictive effects of platelet-to-lymphocyte ratio on neonatal thrombocytopenia in primary immune thrombocytopenic mothers: a retrospective cohort study

Background Primary immune thrombocytopenia (ITP) can increase the risk of neonatal thrombocytopenia (NT). This study aimed to investigate the key factors for predicting the risk of NT. Methods Data were retrospectively collected from all pregnant women with ITP from 2015 to 2021. Newborns were divided into two groups according to the presence or absence of NT. The parameters between the two groups were then compared. Next, the correlation between maternal platelet-to-lymphocyte ratio (PLR) and neonatal platelet count was analyzed by logistic regression and generalized additive model. Additionally, the relationships among the platelet counts of siblings were also determined. Results A total of 147 maternal cases were included. NT was observed in 46 (31.72%) neonates. A history of previous children with NT appeared to have predictive value for NT (OR 16.484, 95% CI 2.212–122.858, P < 0.001), as the nadir gestational platelet (OR 0.958, 95% CI 0.93–0.988, P < 0.001). Correlation analysis of platelet count on postnatal day 1 and the nadir platelet count in 36 sibling neonates showed a positive correlation ( r =0.684, P <0.001; r =0.900, P <0.05). PLR was divided into 3 groups via tertiles, and the incidence of NT was dramatically higher in the group with lower PLR during the second and third trimesters than in the other two groups (48.5% vs 33.3% vs 22%, P <0.05; 50% vs 21.3% vs 26.7%, P <0.001). Moreover, the risk of NT was markedly higher in the first trimester (PLR < 78.51; OR 0.975, 95% CI 0.951–0.999, P <0.05) and the second trimester (PLR < 20.41; OR, 0.899, 95% CI 0.820–0.985, P <0.05) compared to the third trimester. Conclusion Our findings suggest that a history of previous children with NT is a significant factor for predicting NT in subsequent pregnancies. PLR in the first, second and third trimesters can also be used as a reference to predict NT risk.