Abstract Number: LPB0046
Meeting: ISTH 2021 Congress
Background: Previous literature investigating the effect of the blood group on the development of postpartum haemorrhage (PPH) is controversial. It is known that O blood group subjects carry lower levels of Von Willebrand Factor (VWF) and consequently lower levels of factor VIII, but its effect on the risk of PPH in case of thrombocytopenia during delivery is not known.
Aims: To define whether blood group O may strengthen the risk of PPH in thrombocytopenic women.
Methods: We performed a multicentre retrospective study. We enrolled consecutive women undergoing vaginal delivery or caesarean section with moderate/severe thrombocytopenia, without prophylactic platelet transfusions and without congenital thrombocytopenia or an already known immune thrombocytopenia (ITP). Exclusion criteria were the presence of a congenital bleeding disorder, ongoing anticoagulant therapy or the presence of cancer. Women with more than 150.000/µL platelets at delivery were selected as controls and matched for age, type of birth and ethnicity. Blood group was determined in each participant. Odds ratios (ORs) with their 95% confidence intervals (95%CI) were calculated as risk estimates. The analyses were repeated after stratifying for the O/non-O blood group.
Results:
| Table 1. | Platelets< 100.000/µL | Platelets> 150.000/µL | p | |
| Blood group | O | 44 (47%) | 39 (40%) | p=0.46 |
| non-O | 50 (53%) | 55 (60%) | ||
|
Platelets/µL
|
90000 (79000-97000) |
229000(198000 – 260000)
|
<0.01 | |
| Haemoglobin g/dl | 11.4 (10.1 – 12.3) | 11.4 (10.8 – 12.1) | p=0.15 | |
| Fibrinogen mg/dl | 429 (374 – 479) | 463 (402 – 524) | <0.01 | |
| Blood loss (ml) | 500 (300 – 1000) | 300 (200 – 500) | <0.01 | |
| Red Blood Cell Transfusions | 15 (16%) | 1 (1%) | <0.01 | |
| Peripartum hysterectomy | 1 (1%) | 0 | – | |
| Deaths | 0 | 0 | – | |
| PPH (number, percentage) | 37 (37%) | 10 (10%) | <0.01 |
Table 1: Demographic, obstetrical and laboratory characteristics of the study population. Comparison between thrombocytopenic and non-thrombocytopenic women is shown. Dichotomous variables are expressed as numbers and percentages; continuous variables as median and interquartile range (IQR). Statistical analysis has been performed using chi-square test for dichotomous variables and Student’s t-test for continuous variables. PLT, platelet count; ITP, immune thrombocytopenia; HELLP syndrome, Hemolysis elevated liver enzymes and low platelets count syndrome; PPH, postpartum haemorrhage; p, p-value.
Ninety-four thrombocytopenic women and 94 controls were enrolled in the study. The rate of PPH was significantly higher in thrombocytopenic women than in controls (37% vs 10%, p<0.001); a higher risk of PPH was observed in the thrombocytopenic group when compared to the control group (OR 5.47; 95%CI 2.4-12.4). When we stratified the patients into O and non-O blood groups carriers, we found that carrying blood group O confers a higher risk of developing PPH in thrombocytopenic women (OR 12.7; 95%CI 2.9 – 55.3) than in healthy controls (OR 3.2; 95% CI 1.1 – 9.5).
Conclusions:
| PPH | no PPH | crude OR(95%CI) | p-value | ORadj 1 (95%CI) | p-value | ORadj 2 (95%CI) | p value | |
| Thrombocytopenic | 35 | 59 | ||||||
| Healthy controls | 10 | 84 | 4.98 (2.3 – 10.8) | <0.01 | 5.47 (2.4-12.4) | <0.01 | 4.5 (1.9 – 10.8) | <0.01 |
| Thrombocytopenic O | 20 | 24 | ||||||
| non-O | 15 | 35 | 7.3 (2.2 – 24.0) | <0.01 | 12.7 (2.9 – 55.3) | <0.01 | 13.3 (2.2 – 82.2) | <0.01 |
| Healthy controls O | 4 | 35 | ||||||
| non-O | 6 | 49 | 3.5 (1.2 – 9.9) | 0.01 | 3.2 (1.1 – 9.5) | 0.03 | 2.7 (0.8 – 8.7) | 0.09 |
| total | 94 | 94 |
Table 2: Analyses of postpartum haemorrhage risk expressed in the entire cohort of patients and then stratified for O/non-O blood group. Crude OR, crude Odds Ratio; OR adj 1, crude OR adjusted for matching factors and confounders (age, ethnicity, mode of delivery); OR adj 2, crude OR adjusted for age, ethnicity, mode of delivery and other risk factors for PPH (nulliparity, placental disorders, labour induction, gestational age < 32 weeks, fetal macrosomia); Ref, reference; Ter, tertile; p, p-value; PLT, platelets; PPH, postpartum haemorrhage.
Our study shows that the blood group O phenotype is a strong risk factor for PPH if associated with a platelet count below 100.000/µL at delivery.
To cite this abstract in AMA style:
Arcudi S, Ronchi A, Capecchi M, Ossola MW, Mancini I, Marconi AM, Podda G, Artoni A. The Impact of the ABO Blood Group on Postpartum Haemorrhage Risk among Women with Thrombocytopenia [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/the-impact-of-the-abo-blood-group-on-postpartum-haemorrhage-risk-among-women-with-thrombocytopenia/. Accessed August 16, 2022.« Back to ISTH 2021 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/the-impact-of-the-abo-blood-group-on-postpartum-haemorrhage-risk-among-women-with-thrombocytopenia/