Results
During the study period 667 fetuses met the inclusion criteria (on a total of 12.250 NT tests). Mean maternal age was 35.64 ± 3.44 years, 617 (92.92%) were spontaneous pregnancies while 47 (7.08%) pregnancies were conceived by assisted reproductive technology. All fetuses were assessed by ultrasound follow up scans, while CVS or amniocentesis were performed in 288 (43.37%). For children with normal paediatric examination at birth, mean age at the time of follow up was 2.65 years (range 4 months-6 years). There was a live birth of a healthy fetus in 500 (74.96%) cases. The outcome was unfavourable in 167 (25.44%) cases: there were 90 (13.49%) cases of chromosomal abnormalities/genetic syndromes, of which 45 (50%) were trisomy 21, 57 (8.55%) cases of major malformations of which 23 (3.45%) were cardiac, 13 (1.95%) cases of neurodevelopmental delay. In 6 cases a second trimester miscarriage or IUFD occurred in fetuses with no detected abnormalities (0.90%). There was 1 (0.15%) case of metabolic disease (severe growth hormone (GH) deficiency). Details regarding postnatal outcome including the time of diagnosis (prenatal or postnatal) are reported in Table 2.
Details regarding each case of chromosomal abnormalities and genetic syndromes are reported in Table S1. Major malformations and other unfavourable outcome are listed in Table S2, cases of neurodevelopmental delays are listed in Table S3.
The incidence of chromosomal abnormalities/genetic syndromes and major malformations were significantly higher in our cohort (OR 6.99 (IC 95% 4.33 - 11.28), p<0.001 and OR 17.77 (IC 95%7.22 - 43.75), p<0.001 respectively) compared to the general population. Conversely, the incidence of neurodevelopmental delay was not increased (OR of 0.64 CI 95% 0.33 - 1.24 p=0.185) (Table 3 - Figure 1).