Extrinsic Coagulation Pathway Selectivity Of Plateletcrit And Platelet Count In Normal Pregnancy: A Cross-Sectional Study In Ibadan, Nigeria

Abstract

The relationship between platelet morphological indices and coagulation pathway activity during pregnancy remains incompletely characterised, particularly in sub-Saharan African populations where population-specific haematological norms are limited. This study investigated pathway-selective associations between five platelet indices and three coagulation markers across the three trimesters of normal singleton pregnancy in a Nigerian cohort, with specific focus on whether plateletcrit demonstrates selective coupling to the extrinsic coagulation pathway. A cross-sectional design was employed involving 216 healthy pregnant women (56 in the first trimester, 82 in the second, and 78 in the third) alongside 50 non-pregnant controls recruited from public hospitals in Ibadan, Nigeria. Platelet indices—including platelet count, plateletcrit (PCT), mean platelet volume (MPV), platelet distribution width (PDW), and platelet-large cell ratio (P-LCR)—were measured using an automated haematology analyser, while prothrombin time (PT), international normalised ratio (INR), and activated partial thromboplastin time (APTT) were determined manually. Pearson correlation analysis with 95% confidence intervals and Bonferroni correction (adjusted α = 0.0033) was performed, with Spearman analysis used for sensitivity testing. Plateletcrit showed significant positive correlations with PT (r = 0.252, 95% CI: 0.121–0.374, P < 0.001) and INR (r = 0.259, 95% CI: 0.129–0.381, P < 0.001), while platelet count also correlated with PT (r = 0.230, P = 0.001) and INR (r = 0.248, P < 0.001), with all associations remaining significant after correction. No platelet index demonstrated significant correlation with APTT, and PDW, MPV, and P-LCR showed no meaningful relationships with any coagulation markers; these findings were consistent in Spearman analysis. Overall, the results indicate that plateletcrit and platelet count exhibit selective association with extrinsic coagulation pathway markers (PT and INR) during normal pregnancy, while remaining independent of intrinsic pathway activity. This novel observation in a West African obstetric population suggests that total platelet mass co-varies with extrinsic coagulation efficiency across gestation and highlights the potential utility of plateletcrit as an adjunctive haemostatic monitoring parameter in resource-limited antenatal settings.