[Possibilities for modifying risk factors for chromosome abnormalities--advantages of the so-called "triple" marker studies in comparison with pure "maternal age screening"].

We have offered the so-called "triple-marker screening" since May 1991 to all patients who came for prenatal care and did not select an invasive procedure primarily. First evaluation of 5210 cases revealed that 3.7% were test-positive for neural tube defects, 13.8% for Down's syndrome and 0.5% for both at the same time. The explanation for the comparatively high "test-positive" rate of 13.5% is the maternal age distribution with the median at 31.4 years. The highest number of women selecting triple-marker determinations was in the age group of 35 years. We detected 16 cases of Down's syndrome and in this group the majority of women was below 35 years. The decision of women to have an invasive procedure was obviously very much influenced by the actual risk assessment, because amniocentesis was chosen by 72/85 (84.8%) of women with a risk of more than 1:50, 192/290 (66.2%) of women in the risk category of 1:51 to 1:200 and 182/333 (54.6%) in the risk category of 1:201 to 1:400. The follow-up is not yet complete, but there is already good evidence for the efficiency of the screening program. Triple-marker screening also proved predictive in 10 cases of trisomy 18 and 8 cases of triploidy in this series. As a cut-off value we chose the risk of 1:386 which is equivalent to the odds of a 35 year old to have a child with Down's syndrome at birth.(ABSTRACT TRUNCATED AT 250 WORDS)