RESUMO
To study whether spontaneous preterm birth [SPB] is associated with maternal-newborn ABO blood phenotype pairs. We conducted a retrospective case-control study in the Department of Pediatrics, King Abdulaziz Hospital, Al-Ahsa, Kingdom of Saudi Arabia. A total of 631 live singleton SPBs [<37 weeks] between August 2005 and May 2011 formed the case group. A total of 2,204 live singleton term births [>/= 37 weeks] between May 2008 and April 2009 formed the control group. We extracted data on the mothers and their newborns from our neonatal electronic database and delivery room log book. We extracted ABO blood phenotypes using Cerner's Lab Information Software. We used a Chi square test to study the association between SPB and maternal-newborn ABO pairs. We used a combination of maternal-newborn A-A, B-B, AB-AB, and O-O pairs as the reference group. We used a binary logistic regression analysis to adjust for 6 established risk factors for SPB. Spontaneous preterm birth was associated with only maternal-newborn pairs B-A [odds ratio: 2.67, 95% confidence interval: 1.35-5.24, p=0.003] and AB-B [odds ratio: 1.97, 95% confidence interval: 1.04-3.74, p=0.04]. Both associations remained significant in the regression analysis. Spontaneous preterm birth is associated with maternal-newborn B-A and AB-B pairs. This finding requires further confirmatory and exploratory study as it could reduce SPBs.