Additional benefits of first trimester screening.

The goal of first trimester screening for aneuploidy is to provide patients their risk assessment for fetal Down syndrome. Nonetheless, it has been noted that combined screening offers physicians and patients other important pregnancy information. For example, first trimester ultrasound results in accurate pregnancy dating and enables the early diagnosis of multiple gestations during the period when amnionicity and chorionicity is best discerned. It also detects a limited number of fetal anatomical abnormalities, affording patients time to make decisions regarding the management of their pregnancies. A cystic hygroma, one of the most powerful ultrasound markers for fetal aneuploidy, can be detected on first trimester ultrasound. An enlarged nuchal translucency may identify fetuses at risk for other adverse outcomes and for congenital heart defects. In addition, abnormal first trimester serum markers are associated with adverse pregnancy outcomes, and knowledge of these abnormalities may help with patient counseling and management.