STRATEGIES FOR ANTENATAL DETECTION OF DOWNS-SYNDROME

Aim-To predict the effect of maternal serum screening and fetal echoca rdiography on the birth prevalence of Down's syndrome. Methods-The out come of all Down's syndrome pregnancies in the Northern Health Region between 1985 and 1991 was retrospectively ascertained. The number and outcome of all Down's syndrome pregnancies were used to define a theor etical population which would exist in the absence of screening. Publi shed reports were used to predict the effects of screening strategies. Results-Down's syndrome was identified in 412 pregnancies of which 31 5 (76%) resulted in live birth. A theoretical population with no anten atal screening would be expected to produce 31 stillbirths and 381 (92 %) live births affected by Down's syndrome. In the same population a p rogramme of maternal serum screening and fetal echocardiography would lead to 155 and 14 terminations, respectively, and when combined, woul d reduce affected live births to 229 (56%). Conclusions-Even if matern al serum screening and fetal echocardiography achieve their predicted potential, around half of all pregnancies affected by Down's syndrome will result in live born babies.