The objective of this study was to determine the prevalence, adverse pregnancy complications, and optimal management of pregnancies complicated by bleeding in the second half of pregnancy of an unknown origin (ABUO). A MEDLINE search from 1966 through November 2004 using the search terms "antepartum hemorrhage" or "hemorrhage" or "uterine hemorrhage" and "pregnancy complications" and "cardiovascular complications" and "second trimester pregnancy" or "third trimester pregnancy" was undertaken. The inclusion criteria focused on bleeding not resulting from placenta previa or abruption or to any known cause. The MEDLINE search provided 24 abstracts for review with 9 studies meeting the inclusion criteria The prevalence of ABUO was 2%. The likelihood of antepartum hemorrhage and delivery before 37 weeks was significant with an odds ratio (OR) of 3.17 and 95% confidence interval (CI) of 2.76-3.64. The risk of intrauterine fetal demise was significantly increased in women with ABUO (OR, 2.09; 95% CI, 1.43-3.06). The association between ABUO and fetal anomalies was increased with an OR 1.42 (95% CI, 1.07-1.87). Only one study with a small sample size (N = 48) compared the outcomes of women using Doppler studies of the umbilical and uterine arteries and biophysical profiles. No differences were observed in the women undergoing antenatal testing and the women not undergoing antenatal testing. The prevalence of ABUO is 2%. Preterm delivery, stillbirth, and fetal anomalies appear to be increased in these pregnancies. Antenatal testing may be of limited value in their management.
Target audience: Obstetricians & Gynecologists, Family Physicians Learning Objectives: After completion of this article, the reader should be able to explain the prevalence of antepartum bleeding of unknown origin (ABUO) in confronting a patient with ABUO, summarize the types and frequency of adverse pregnancy outcomes in ABUO, and recall the limited usefulness of antenatal testing in patients with ABUO.