Expected,prenatally discovered,and born cases of Down syndrome in Denmark during the period 1980–1998

In order to elucidate the consistency between generally used age-dependent risk values for Down syndrome (DS) and estimates of the probability of miscarriage in Down pregnancies we have compared expected numbers with estimated numbers of births with DS in Denmark had no intervention at all been carried out. The expected numbers were calculated from the distribution of newborn children according to maternal age combined with the age-related risk of DS. The estimated numbers of children that actually would have been born without any intervention were estimated from observed numbers of cases of DS, i.e. the cases born plus – with corrections because of the high probability of miscarriage in DS pregnancies – a proportion of those cases discovered prenatally. The analysis was carried out separately for mothers aged 35 years or older and for younger mothers. We found a high degree of compatibility between expected and estimated numbers, probably with a minor underestimation of the expected values for the older mothers. The performance of DS screening in Denmark in the period under consideration (1980–1998) is discussed in relation to the figures presented. Despite the fact that 11.8% of all pregnancies were subjected to an invasive diagnostic procedure, only about 38% of all births with DS were prevented. This means that in the period 1990–1998, reluctance to accept serological screening has indirectly resulted in the birth of almost 300 cases of DS in Denmark and at the same time the miscarriage of an unreasonable high number of normal fetuses. Copyright © 2001 John Wiley & Sons, Ltd.     

Nature and frequency of chromosomal abnormalities in pregnancies with abnormal ultrasound findings: An analysis of 117 cases with review of the literature

During a 7-year period, 117 fetal karyotypes were available from 131 genetic amniocenteses. These procedures were performed between 14 and 37 weeks' gestation for the following abnormal ultrasound findings: (1) intrauterine growth retardation (IUGR)—61 cases; (2) fetal malformation—71 cases; and (3) amniotic fluid volume (AFV) abnormality—60 cases. Chromosomal abnormalities were identified in 19 cases (16.2 per cent). Aneuploidy was 2.5 times as frequent in the presence of malformations than in their absence. No correlation was demonstrated between specific fetal malformations and specific chromosomal abnormalities. Aneuploidy was also twice as frequent in the presence of symmetrical IUGR than in its absence. No chromosomal abnormalities were found among eight cases of asymmetrical IUGR. Four cases of aneuploidy presented with isolated IUGR, three of these involving the X chromosome. The frequency of aneuploidy was the same with or without abnormalities of AFV (14.3 versus 16.4 per cent). No chromosomal abnormality was found associated with isolated AFV abnormalities.