OP18.07: Pre‐ and postnatal diagnosis of fetal trisomy in the north‐east of the Netherlands

To describe the diagnostic pathway for 175 consecutive cases of trisomy 21, 18 or 13. Prenatal and postnatal data were examined from 118 consecutive cases of trisomy 21 and 57 cases of trisomy 18 or trisomy 13 with an estimated date of delivery was between 1-6-2008 and 1-6-2010. In 73 (42%) of 175 trisomic pregnancies a first trimester (FTS) scan was performed and in 62 (85%) of these cases an anomaly was diagnosed or the risk of the combined test was increased. In 61 (35%) trisomic pregnancies FTS was declined but a second trimester scan (STS) was performed which revealed anomalies in 38% of cases with trisomy 21 and a 83% with trisomy 18 or 13. In 18 (10%) of the affected pregnancies neither invasive testing nor FTS or STS were performed. The first trimester scan (FTS) and the combined test (CT) are effective in detecting fetal trisomy. If screening is postponed to the second trimester the detection of trisomy 21 is less than 50%; fetuses with trisomy 18 or 13 are almost always identified but not always before the legal limit for abortion.