Maternal serum screening for Down syndrome in women aged 40 years and over.

Two hundred and thirty-nine women aged 40 years were booked for delivery at Kettering General Hospital from 1992 to 1997. Six women were not eligible for the triple test (TT) as they booked too late. Eighty-eight women declined TT. The reasons were; fear and anxiety about the risk of miscarriage associated with amniocentesis if the test result were a high risk (70.5%), worries about the false negative result associated with the TT (20.5%) and reluctance to terminate the pregnancies if the fetus were abnormal (9%). One hundred and forty-five women (62.2%) elected for TT of whom 91 (62.8%) had received a high risk results. Of the women who received a high-risk result 61/91 (67%) had an amniocentesis. The study provides an accurate probability of receiving a high risk TT screening in women aged 40 years and highlights the need for a more sensitive screening test or a less invasive diagnostic test for the detection of Down syndrome.