Trimester-specific Platelet and Coagulation Changes in Normal Pregnancy: A Cross-sectional Study in Nigerian Women
B. E. Adesina
*
Department of Haematology and Blood Transfusion Science, Faculty of Medical Laboratory Science, Achievers University, P.M.B. 1030, Owo, Ondo State, Nigeria and Department of Haematology and Blood Transfusion Science, Faculty of Health Science, Lead City University, Ibadan, Oyo State, Nigeria.
M. A. Muhibi
Department of Haematology and Blood Transfusion Science, Faculty of Medical Laboratory Science, Achievers University, P.M.B. 1030, Owo, Ondo State, Nigeria and Department of Medical Laboratory Science, Edo State University Uzairue, Edo State, Nigeria.
O. T. Oke
Department of Haematology and Blood Transfusion Science, Faculty of Medical Laboratory Science, Achievers University, P.M.B. 1030, Owo, Ondo State, Nigeria.
F. O. Amusan
Department of Medical Laboratory Science, Edo State University Uzairue, Edo State, Nigeria.
A. H. Oniye
Department of Haematology and Blood Transfusion Science, Faculty of Health Science, Lead City University, Ibadan, Oyo State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Background: Normal pregnancy is characterized by a physiological shift towards hypercoagulability that increases maternal venous thromboembolism (VTE) risk, yet detailed, integrated characterization of platelet and coagulation changes across gestation is lacking in Nigerian women.
Aim: This study aimed to (i) describe trimester‑specific changes in platelet indices and coagulation parameters in healthy singleton pregnant women compared with non‑pregnant controls and (ii) quantify inter‑compartmental correlations as evidence of coordinated thrombotic priming.
Study Design: Hospital‑based cross‑sectional case‑control study.
Place and Duration of Study: Three public antenatal clinics in Ibadan, Oyo State, Nigeria, between March and August 2025.
Methodology: We recruited 216 healthy singleton pregnant women, stratified equally into first (T1; 1–12 weeks), second (T2; 13–28 weeks), and third (T3; 29–40 weeks) trimesters (n=72 per group), and 50 non‑pregnant controls. Platelet indices [platelet count, platelet distribution width (PDW), mean platelet volume (MPV), platelet‑large cell ratio (P‑LCR), plateletcrit (PCT)] were measured using an automated haematology analyser (Sysmex KX‑21N). Prothrombin time (PT), international normalized ratio (INR) and activated partial thromboplastin time (APTT) were determined using the manual tilting‑tube method with commercial reagents. Data were analysed with one‑way ANOVA and Tukey’s post‑hoc tests; Pearson correlation quantified associations between platelet and coagulation parameters. Results are reported with exact p‑values, 95% confidence intervals (CI) and effect sizes. The study adhered to the STROBE guideline for cross‑sectional studies.
Results: Platelet count declined significantly from controls (212.72±35.49×10⁹/L) to T2 (177.90±42.05×10⁹/L), with partial recovery in T3 (187.23±45.04×10⁹/L) (F=7.06, η²=0.08, p<0.001). PCT showed a similar decrease (F=4.05, η²=0.05, p=0.008). Conversely, MPV increased (F=4.74, η²=0.06, p=0.003) and P‑LCR rose (F=5.01, η²=0.06, p=0.002), indicating qualitative platelet activation despite numerical decline. PT and INR were significantly shorter/lower in pregnant women compared with controls (PT: F=4.07, η²=0.05, p=0.008; INR: F=4.89, η²=0.06, p=0.003), whereas APTT remained unchanged (F=0.56, p=0.643), suggesting selective extrinsic pathway amplification with preserved intrinsic pathway function. Among pregnant participants, platelet count correlated positively with PT (r=0.230, 95% CI 0.097–0.355, p=0.001) and INR (r=0.248, 95% CI 0.117–0.372, p=0.001); PCT showed similar associations, whereas MPV, P‑LCR and PDW did not correlate significantly with PT, INR or APTT (all p>0.05). Trimester‑specific reference intervals (mean±2SD) were generated for all parameters.
Conclusion: Normal singleton pregnancy in this Nigerian cohort is characterized by coordinated haemostatic remodeling, with platelet quantitative depletion coexisting with morphological activation and selective extrinsic coagulation pathway amplification. The novel inter‑compartmental correlations between platelet mass indices and PT/INR provide mechanistic evidence of integrated thrombotic priming rather than independent parallel changes. The trimester‑specific reference intervals derived here are directly applicable to obstetric haematology practice in Nigeria and may prevent misclassification of physiologic gestational alterations as pathology.
Keywords: Normal pregnancy, platelet indices, prothrombin time, activated partial thromboplastin time, haemostasis, thrombotic priming