ACOG Practice Bulletin No. 27: Clinical Management Guidelines for Obstetrician-Gynecologists. Prenatal diagnosis of fetal chromosomal abnormalities.

The prevalence of chromosomal abnormalities in clinically recognized early pregnancy loss is approximately 50% (1). Aneuploid fetuses account for 6-11% of all stillbirths and neonatal deaths (2). Chromosome defects compatible with life but causing significant morbidity occur in 0.65% of newborns, and another 0.2% have structural chromosomal rearrangements that will eventually affect reproduction (3). Although it is not possible to identify all aneuploidies antenatally, screening and diagnostic programs to detect the most common autosomal trisomy in liveborn infants, Down syndrome, are well established. This document will provide clinical management guidelines for the prenatal detection of these aneuploidies.