ObjectiveTo investigate obstetricians' genetic knowledge base and practice trends.MethodsA questionnaire survey was sent to 1003 ACOG Fellows, 554 (55%) of whom responded. Results from the 446 respondents practicing obstetrics are reported.ResultsThe majority of obstetricians surveyed (85.6%) reported completing standardized genetic-history forms for prenatal patients, and about half (48%) performed their own invasive diagnostic procedures. Most (87%) had access to genetic counselors. For aneuploidy risks associated with advanced maternal age, up to 69% of respondents provided at least some patient counseling in their offices. Physician knowledge of risk assessment and diagnostic testing in the areas of aneuploidy and neural tube defects was very good; however, for single-gene disorders such as cystic fibrosis, Tay-Sachs disease, and sickle cell disease, correct risk assessment or appropriate test selection presented difficulties for at least half of the respondents. Respondents cited the rapidity of changes in genetic testing as the greatest obstacle to providing genetic information to patients.ConclusionObstetricians' knowledge of inheritance and test selection pertaining to single-gene disorders was more limited than that for aneuploidy and neural tube defects. Comparable deficits were noted in patient-education efforts for single-gene disorders.