Increased prenatal detection of 22q11.2 deletion and 22q11.2 duplication after introduction of nationwide prenatal screening for trisomy 21, trisomy 13, and trisomy 18

To evaluate time of diagnosis of 22q11.2 deletion and 22q11.2 duplication as well as trisomies 21, 13, and 18 before and after introduction of a prenatal screening program including combined first-trimester screening (cFTS) for the trisomies in Denmark in 2004.Cross-sectional, population-based register study employing The Danish Cytogenetic Central Register. Proportions of cases diagnosed 1998-2004 and 2005-2017 were compared before 14+0 and 22+0 weeks and birth (prenatal cases) or up to 1 or 10 years of age (postnatal cases).In total, 4562 cases were included. From 1998-2004 to 2005-2017, the proportion of 22q11.2 deletion cases identified prenatally increased from 4.3% (95% CI: 0.9-12.0%) to 27.3% (21.2-34.0%), while for 22q11.2 duplication an increase from 0/6 to 26/87 (prenatal cases/all cases) was observed. Similarly, proportions of trisomies 21, 13, and 18 detected before birth increased. A greater proportion of the studied conditions was identified earlier in pregnancy, but not generally earlier in the postnatal course.Proportions of 22q11.2 deletion and 22q11.2 duplication identified prenatally increased after introduction of a prenatal screening program not aimed specifically to identify these conditions,. A greater proportion of all cases were detected earlier in pregnancy, but not earlier postnatally, following introduction of screening.