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Maternal ABO blood group and stillbirth: a prospective cohort investigation.

OBJECTIVE
To determine whether maternal ABO blood group is associated with risk of stillbirth.


STUDY DESIGN
Prospective cohort. Risk of stillbirth among women of blood group A, B and AB was compared to that of women with group O by logistic regression and survival analysis.


RESULTS
There were 1,018 stillbirths in 52,605 pregnancies (19.4 per thousand). Stillbirths occurred in 19.2/ 1,000 pregnancies in group O, 19.8/1,000 pregnancies in group A (race-adjusted odds ratio [OR] vs. group O of 1.1, 95% confidence interval [CI] 0.9-1.2), 19.4/1,000 to group B (race-adjusted OR vs. group O of 1.0, 95% CI 0.8-1.2), and 17.2/1,000 pregnancies in group AB (race-adjusted OR vs. group O of 0.9, 95% CI 0.6-1.2) women. Survival analysis, accounting for varying times at entry to prenatal care, produced similar results. Results were similar for singleton births, stillbirths < 24 weeks' and > or = 24 weeks' gestation, and antepartum and intrapartum stillbirths considered separately.


CONCLUSION
Maternal ABO blood group was not associated with stillbirth.