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The cytogenetic results of 1500 chorionic villus samples (CVS) are presented. In these 1500 samples, 23 samples (1.5 per cent) could not be provided with a diagnosis because of laboratory failure. This failure rate dropped from 3 per cent in the first 500 samples to 0.2 per cent in the last 500. In the remaining 1477 samples, 58 (3.9 per cent) chromosomal aberrations were found. Of these, 21 (36 per cent) proved not to represent the karyotype of the fetus proper. Predictive values of (different groups of) chromosomal aberrations in CVS are calculated. The impact of (differences between) the predictive value for some major chromosomal aberrations is discussed. A tissue- and chromosome-specific selection mechanism is postulated.

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Objective To provide an overview of invasive prenatal diagnosis in the Netherlands and to analyse trends.Methods Annual results from all centres for invasive prenatal diagnosis in the Netherlands over the period 1991-2000 were combined and described, with particular emphasis on indications, abnormal results, type of invasive procedures, and terminations of pregnancy. ResultsThe percentage of invasive prenatal diagnosis increased from 5% of births in 1991 to 6% in 1996 and subsequently remained at that level. During the study period, the number of pregnant women aged 36 and older increased by 70%, but the number of procedures performed because of maternal age remained stable. The detection rate for abnormal results was 2-3% for maternal age and rose from 9 to 13% for other indications. Other trends during the study period included a relative decrease in cordocentesis (−82%) and chorionic villi biopsy (−18%) in favour of amniocentesis (+48%), and a strong decrease in the number of amniocentesis procedures for increased risk of neural tube defect. In 71% of the cases with abnormal results, the pregnancy was terminated. ConclusionThere was a significant decrease in the percentage of pregnant women aged 36 or older who underwent invasive prenatal diagnosis without previous screening.

Schwangerschafts Protein 1 (SP1), being a placental protein appearing in the maternal circulation early in pregnancy, has been investigated as a potential marker for Down syndrome in the first trimester. Our study compared SP1 levels in 15 pregnancies with a Down syndrome fetus and 97 matched controls. Although the median MoM in Down syndrome pregnancies (0·49) was lower than in controls, its use as a marker added very little to the detection rate above the maternal age alone. Copyright © 1998 John Wiley & Sons, Ltd.