This was an analytical cross-sectional study, conducted in the Department of Obstetrics and Gynecology of the Yaoundé Central Hospital (YCH), a national referral center, a setting that increases the local prevalence of hemorrhagic pathological pregnancies relative to primary-care facilities. Recruitment and data collection took place between February and May 2025.

All pregnant women presenting with a hemorrhagic pathological pregnancy and received in the department during the study period were eligible. Inclusion criteria were a confirmed hemorrhagic pathology of pregnancy and informed, voluntary consent to participate. Women who declined participation were excluded.

The dependent variables were the type of hemorrhagic pathology of pregnancy (the leading cause of maternal mortality worldwide according to the World Health Organization, accounting for approximately 27% of deaths [3]) and VWF:Ag concentration. The independent variable was ABO blood group, a stable genetic determinant of baseline plasma VWF concentration; individuals with blood group O are known to have physiologically lower baseline VWF levels than non-O individuals. The primary comparison of interest, specified a priori, was the difference in mean VWF:Ag concentration between blood-group-O and non-O women in the overall sample (Table 1). Comparisons stratified by pathology type, by presence of fetal complications, and by disease-severity subgroup (Tables 2-4) were secondary, exploratory analyses intended to generate hypotheses for confirmatory testing in larger studies; they were not adjusted for multiple comparisons, and their p-values should be interpreted accordingly.

Data were collected using a structured questionnaire, supplemented by medical records and laboratory results. A 5 mL venous blood sample without anticoagulant was drawn aseptically from the antecubital vein of each patient on arrival, then centrifuged at 3500 rpm for 5 minutes; serum was aliquoted into sterile cryotubes and stored at −20˚C until analysis. VWF:Ag was measured by sandwich ELISA (Biofine reagent), a kit validated by the manufacturer for use with serum. The concentration of each sample was read from a calibration curve constructed according to the manufacturer’s instructions. The reference range for VWF:Ag was taken as 50% - 150% (0.5 - 1.5 IU/mL).

Recruitment was consecutive and based on convenience, which may have introduced selection bias, and the single-center referral setting may limit generalizability to non-referral facilities. Eleven eligible women declined participation because of needle phobia; if this refusal was associated with pathology or severity, non-response bias cannot be excluded. Subgroup sample sizes were small for some pathologies (e.g., postpartum hemorrhage, n = 4), which limits the precision of subgroup estimates. A gestational age (mean ± SD or median [IQR]) at sampling for each diagnostic group, and the interval between symptom onset/admission and blood sampling relative to delivery; also state, for each group, the proportion who had already received a blood transfusion, intravenous fluid resuscitation, or other treatment (e.g. magnesium sulfate, uterotonics) before the sample was drawn, since these factors can independently affect VWF:Ag concentration and their imbalance across groups would be a potential confounder.

No prior sample size calculation was performed. During the study period, 834 pregnant women were received in the department; 743 did not meet the inclusion criteria and were excluded, leaving 91 women with a hemorrhagic pathological pregnancy. Of these, 11 declined consent because of needle phobia, yielding a final analytic sample of 80 participants.

VWF:Ag concentration was analyzed as a continuous variable (%, converted to IU/mL). ABO blood group was dichotomized as O versus non-O (A, B, AB). Within each pathology, disease severity was further categorized using standard clinical classifications (the Sher classification for retro-placental hematoma; grade for hemorrhagic placenta previa; severe versus mild for pre-eclampsia and postpartum hemorrhage; and hemodynamic stability for ruptured ectopic pregnancy). The diagnostic and severity criteria actually applied in this study, e.g.: pre-eclampsia diagnosed as new-onset hypertension ≥ 140/90 mmHg after 20 weeks’ gestation with proteinuria or another severe feature, graded severe when blood pressure ≥ 160/110 mmHg or a severe feature (thrombocytopenia, hepatic or renal impairment, pulmonary oedema, cerebral/visual symptoms) was present; retroplacental hematoma graded by the Sher classification (grade 2: moderate bleeding with evidence of fetal distress in a live fetus; grade 3: severe bleeding with fetal death, subdivided into 3a without and 3b with coagulopathy); hemorrhagic placenta previa graded 1 - 4 by the degree of os coverage (low-lying to complete); postpartum hemorrhage defined per WHO criteria (blood loss ≥ 500 mL after vaginal birth or ≥1000 mL after caesarean within 24 hours), classified as severe when blood loss exceeded 1000 mL or hemodynamic instability was present; and ruptured ectopic pregnancy classified as hemodynamically unstable when presenting with systolic blood pressure < 90 mmHg, heart rate > 100 bpm, or clinical signs of hypovolemic shock.

Data were entered in Microsoft Excel and analyzed with SPSS version 26.0. Quantitative variables are presented as mean ± standard deviation. The chi-square test was used to compare proportions, and the independent-samples t-test was used to compare mean VWF:Ag concentrations between groups. A p-value < 0.05 was considered statistically significant.

This study complied with the fundamental principles of medical research. Administrative authorization (N˚ 011/25/AR/MINSANTE/SG/DHCY/CM) and ethical clearance (N˚ 0050/CHRERSHC/2025) were obtained prior to data collection, and written informed consent was obtained from all participants.

Table 1.Mean VWF:Ag concentration by ABO blood group among women with hemorrhagic pathological pregnancy (N = 80).

VWF:Ag: Von Willebrand factor antigen; SD: standard deviation; pp: percentage points; CI: confidence interval. Independent-samples t-test with Welch’s correction for unequal variances; mean differences and p-values recalculated from the reported means, SDs, and sample sizes. This comparison was the pre-specified primary analysis; p < 0.05 was considered statistically significant, but this difference did not reach that threshold.

Table 2.VWF:Ag concentration by type of hemorrhagic pathological pregnancy and ABO blood group (N = 80).

VWF:Ag: Von Willebrand factor antigen; SD: standard deviation; pp: percentage points; CI: confidence interval. †Not computed: single observation in the non-O postpartum-hemorrhage subgroup (n = 1). Independent-samples t-test with Welch’s correction for unequal variances, recalculated from the reported means, SDs, and sample sizes. These pathology-stratified comparisons are secondary/exploratory and were not adjusted for multiple comparisons; none reached statistical significance.

Table 3.VWF:Ag concentration by presence of fetal complications among women with hemorrhagic pathological pregnancy (N = 80).

VWF:Ag: Von Willebrand factor antigen; SD: standard deviation; pp: percentage points; CI: confidence interval. Independent-samples t-test with Welch’s correction for unequal variances; mean difference and p-value recalculated from the reported means, SDs, and sample sizes (the original mean difference of 11.62 pp was an arithmetic error; the correct value is 9.93 pp). This comparison did not reach statistical significance.

Table 4.VWF:Ag concentration by disease-severity subgroup within each hemorrhagic pathological pregnancy.

VWF:Ag: Von Willebrand factor antigen; SD: standard deviation; pp: percentage points; CI: confidence interval. Sher grade: classification of retroplacental hematoma severity (grade 3 > grade 2). Independent-samples t-test with Welch’s correction for unequal variances, recalculated from the reported means, SDs, and sample sizes; the postpartum-hemorrhage comparison (n = 2 per subgroup) is reported for completeness but is not statistically meaningful given the minimal sample. These severity-stratified comparisons are secondary/exploratory and were not adjusted for multiple comparisons. *p < 0.05, statistically significant.

Of 834 pregnant women received in the department during the study period, 743 did not meet the inclusion criteria. Of the 91 women identified with a hemorrhagic pathological pregnancy, 11 declined to participate because of needle phobia, leaving 80 women who consented and were included in the final analysis.

Among the 80 participants, 48 (60.0%) had blood group O and 32 (40.0%) had a non-O blood group (A, B, AB). By pathology type, 37 women had pre-eclampsia, 18 had a ruptured ectopic pregnancy, 12 had a retroplacental hematoma, nine had hemorrhagic placenta previa, and four had postpartum hemorrhage. One pre-eclampsia patient (1/37) had incomplete severity documentation and was excluded from the severity-stratified analysis (Table 4), a missing-data pattern considered unrelated to VWF concentration and unlikely to bias the reported comparison.

The prevalence of hemorrhagic pathological pregnancy among all pregnant women received during the study period was 10.9% (91/834). The overall mean VWF:Ag concentration in the 80 participants was 163.60% ± 25.80% (1.64 ± 0.26 IU/mL).

VWF:Ag concentration was higher in women with blood group O (167.44% ± 21.34%) than in non-O women (157.82% ± 30.79%; mean difference 9.62 percentage points, 95% CI −2.94 to 22.18), but this difference did not reach statistical significance using an independent-samples t-test with unequal variances (Welch’s t = 1.54, df = 50.6, p = 0.13) (Table 1, Figure 1).

Figure 1.Mean VWF:Ag concentration (±SD) by ABO blood group among women with hemorrhagic pathological pregnancy (N = 80). Shaded band: normal reference range (50% - 150%).

By pathology type, mean VWF:Ag concentrations differed by blood group as follows (none reaching statistical significance): pre-eclampsia, 160.50% ± 23.79% (O) versus 153.50% ± 34.08% (non-O; 95% CI −14.00 to 28.00; p = 0.50); ruptured ectopic pregnancy, 169.50% ± 20.79% (O) versus 160.20% ± 13.40% (non-O; 95% CI −8.90 to 27.50; p = 0.29); retroplacental hematoma, 182.75% ± 7.47% (O) versus 182.50% ± 8.18% (non-O; 95% CI −11.87 to 12.37; p = 0.96); hemorrhagic placenta previa, 169.25% ± 25.59% (O) versus 157.40% ± 38.39% (non-O; 95% CI −39.00 to 62.70; p = 0.60); and postpartum hemorrhage, 161.66% ± 6.80% (O, n = 3) versus 123.00% (non-O, n = 1), for which a variance-based test could not be computed given the single non-O observation (Table 2).

VWF:Ag concentration was higher in the presence of fetal complications (169.76% ± 24.44%) than in their absence (159.83% ± 26.69%; mean difference 9.93 percentage points, 95% CI −1.45 to 21.31; p = 0.09), a difference that did not reach conventional statistical significance (Table 3, Figure 2).

Figure 2. Mean VWF:Ag concentration (± SD) by presence of fetal complications among women with hemorrhagic pathological pregnancy (N = 80). Shaded band: normal reference range (50% - 150%).

VWF:Ag concentration also varied with disease severity within each pathology category (Table 4). In pre-eclampsia, levels were lower in severe disease (150.01% ± 29.89%) than in mild disease (160.33% ± 11.93%; 95% CI −55.82 to 35.18; p = 0.41), a comparison in which the mild-disease subgroup was very small (n = 2). In ruptured ectopic pregnancy, levels were significantly higher with hemodynamic instability (177.20% ± 9.70%) than with hemodynamic stability (146.33% ± 16.48%; 95% CI 13.53 to 48.21; p = 0.004). In retroplacental hematoma, levels were higher in Sher grade 3 (186.42% ± 4.96%) than in Sher grade 2 (177.40% ± 7.19%; 95% CI 0.13 to 17.91; p = 0.048), a difference of borderline significance. In hemorrhagic placenta previa, levels were higher in grade 2 - 3 disease (177.16% ± 11.65%) than in grade 4 disease (133.67% ± 43.06%; 95% CI −58.54 to 145.52; p = 0.22), which did not reach statistical significance once unequal variances were accounted for. In postpartum hemorrhage, levels were higher in severe cases (159.00% ± 7.07%) than in mild cases (145.00% ± 31.11%; p = 0.64), though with only two observations per subgroup this comparison is not statistically meaningful.

No additional subgroup or sensitivity analyses were performed.