Trimester-specific Variations in Prothrombin Time, Activated Partial Thromboplastin Time, and Platelet Count among Pregnant Women at Adeoyo Maternity Teaching Hospital, Oyo State, Nigeria

Abstract

Background: Pregnancy is associated with physiological changes in haemostasis that may vary across gestation. Aims: To assess prothrombin time (PT), activated partial thromboplastin time (aPTT), and platelet count across the three trimesters of pregnancy and compare these parameters with those of non-pregnant controls among women attending Adeoyo Maternity Teaching Hospital (AMTH), Oyo State, Nigeria, and to contribute towards trimester-specific reference values for antenatal coagulation monitoring. Study Design: Cross-sectional, comparative study. Place and Duration of Study: Antenatal clinic, Adeoyo Maternity Teaching Hospital (AMTH), Ibadan, Oyo State, Nigeria, in collaboration with the Department of Medical Laboratory Science, Lead City University, Ibadan. Methodology: 230 women were studied: 180 pregnant women (60 each in the first, second, and third trimesters) and 50 non-pregnant controls of reproductive age. Ethical approval was obtained from the Ethics Review Committee, Ministry of Health, Oyo State, and written informed consent was obtained from all participants. Venous blood was collected into sodium citrate tubes for PT and aPTT (manual clotting method) and EDTA tubes for platelet count (Sysmex automated haematology analyser). Data were analysed by one-way ANOVA with post hoc Tukey comparison; significance was set at p < 0.05. Results: Mean PT declined significantly across gestation, from 12.59 ± 1.01 s (first trimester) to 11.90 ± 0.84 s (third trimester) (F = 4.288, p = 0.008). Mean aPTT rose from 27.86 ± 3.49 s to 30.88 ± 5.97 s across trimesters, approaching but not reaching significance (F = 2.66, p = 0.0512). Platelet count fell progressively and significantly, from 322.29 ± 176.52 ×10⁹/L to 240.40 ± 74.70 ×10⁹/L, a decline of approximately 25% (F = 13.24, p < 0.0001). Conclusion: Pregnancy in this cohort of Nigerian women was associated with a modest decline in PT and a substantial, progressive decline in platelet count, particularly in the third trimester, while aPTT remained comparatively stable. These findings demonstrate significant trimester-specific differences in coagulation parameters and provide preliminary data to inform the future development of trimester-specific reference ranges and routine coagulation monitoring in antenatal care.