Normal midtrimester (17‐20 weeks) genetic sonogram decreases amniocentesis rate in a high‐risk population.

Abstract

OBJECTIVE: To evaluate a screening protocol using advanced maternal age, triple-marker screening, and genetic sonography. METHODS: We compared adverse chromosomal outcomes of pregnancy in 1556 women referred for increased risk of aneuploidy because of either advanced maternal age or triple-marker test results. Patients were counseled about the results of the triple-marker test and subsequent sonography, which led to a patient decision of whether to pursue amniocentesis. Fetal measurements and structural abnormalities were compared with chromosomal findings. When patients elected amniocentesis, karyotypes were obtained. RESULTS: Genetic sonography reduced the rate of amniocentesis by 61% overall and by 40% when compared with an alpha-fetoprotein profile alone. The sensitivity of sonography combined with the triple-marker screen for the detection of trisomy 21 was 87% compared with 91% for the triple-marker screen alone. CONCLUSIONS: This study confirmed that sonographic findings in a targeted population, in combination with other risk markers (advanced maternal age and triple-marker screening), can be used to assess the risk of aneuploidy. Biometry provides additional information for assessing the risk of aneuploidy. Combining advanced maternal age, serum triple-marker screening, and sonographic screening may provide better risk prediction for use in clinical counseling.