Normal midtrimester (17-20 weeks) genetic sonogram decreases amniocentesisrate in a high-risk population

Objective. To evaluate a screening protocol using advanced maternal age, tr iple-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 tes t results. Patients were counseled about the results of the triple-marker t est and subsequent sonography, which led to a patient decision of whether t o pursue amniocentesis. Fetal measurements and structural abnormalities wer e compared with chromosomal findings. When patients elected amniocentesis, karyotypes were obtained. Results. Genetic sonography reduced the rate of a mniocentesis by 61% overall and by 40% when compared with an a-fetoprotein profile alone. The sensitivity of sonography combined with the triple-marke r screen for the detection of trisomy 21 was 87% compared with 91% for the triple-marker screen alone. Conclusions. This study confirmed that sonograp hic findings in a targeted population, in combination with other risk marke rs (advanced maternal age and triple-marker screening), can be used to asse ss the risk of aneuploidy. Biometry provides additional information for ass essing the risk of aneuploidy. Combining advanced maternal age, serum tripl e-marker screening, and sonographic screening may provide better risk predi ction for use in clinical counseling.