Prenatal chromosomal aberration screening mainly focuses on the identification of the autosomal trisomy of chromosomes 21, 18, and 13 (Down syndrome, Edwards syndrome, and Patau syndrome, respectively). This screening may be often combined with other first-semester screenings to promote earlier detection of other pregnancy complications, including chromosomal aberrations. In the Czech Republic, there is no unified policy for prenatal screening. The main prenatal diagnostic centers provide combined prenatal screening in the first semester, whereas some conduct biochemical screening in the second trimester. Those with positive screening results or abnormal ultrasound are offered invasive diagnostic procedures, such as chorionic villus sampling (CVS) or amniocentesis, along with additional genetic testing. Whereas the number of amniocenteses has declined, the number of CVS is increasing. The aim of this study was to examine the results of chromosomal aberrations screening in a population with a high rate of first-trimester screening and low rate of noninvasive prenatal testing.
This was a population-based study, using data from the National Registry of Congenital Anomalies of the Czech Republic from 2012 to 2016. Included were all cases of prenatally diagnosed chromosomal aberrations. The proportions of the autosomal trisomies and other chromosomal aberrations were calculated and compared. The denominator was the number of live births per year.
A total of 3009 prenatally diagnosed cases of chromosomal aberrations were identified during the study period. The most common aberrations were the major autosomal trisomies (1885 cases [62.6%]). The number of invasive prenatal diagnostic procedures decreased from 11,517 cases (1099.54 per 10,000) to 7042 cases (622.73 per 10,000) during the study period. From 2012 to 2016, the number of prenatally diagnosed major autosomal trisomies increased (329 cases [30.86 per 10,000] vs 423 cases [37.41 per 10,000], respectively; Poisson regression: P = 0.014), and the number of other aberrations decreased (246 cases [23.07 per 10,000] vs 217 cases [19.19 per 10,000], respectively; Poisson regression: P = 0.017). There was a highly statistically significant increase of 57.22% in 2012 to 66.09% in 2016 in the rate of the major autosomal trisomies group (logistic regression: P < 0.001).
The study found that, during a 5-year period, when invasive prenatal diagnostic procedures declined, there was also a decrease in the number of nonmajor chromosomal aberrations. Noninvasive prenatal testing was not shown to impact these data.
