[Indications of fetal chromosome abnormalities in 1st trimester ultrasound].

The measurement of the nuchal translucency and the evaluation of other sonographic signs in the first trimester scan allow a detection rate of 70-80% of aneuploid pregnancies, significantly more than with consideration of the maternal age alone (30%). The sonographic signs include the early growth retardation, deviations of the fetal heart rate, exomphalos, megacystis, holoprosencephaly and enlargement of the cisterna magna. Maternal serum biochemistry alone (PAPP-A and beta-hCG or alpha-fetoprotein, estriol and beta-hCG) detects about 65% of aneuploid pregnancies. The best individual risk estimation is based on maternal age, measurement of the nuchal translucency and the maternal biochemistry.