Antenatal examinations for Down syndrome diagnosis
Down syndrome is one of the most severe fetal damages. Therefore, it is necessary to perform antenatal examinations during pregnancy so as to detect this disorder.
The first phase consists of non-invasive tests – genetic ultrasound, which is performed before the13th week and 6th day of pregnancy along with the mother’s blood biochemical tests. In case of Down syndrome, the sensitivity of the former is about 80%. Much better results provides the combination of genetic ultrasound and PAPP-A test – it allows to detect approximately about 95% of cases. Unfortunately, sometimes there are false positives, which means that the study shows that the fetus has the disadvantage, although in reality the child is healthy. This may be caused by improperly determined first day of pregnancy, protein level or multiple gestation.
The age limit above which it is recommended to perform prenatal examination is 30 – 35 years. The most reliable results are ensured by test of fetal karyotype. Its genetic material can be obtained from mother’s blood in a safe and non-invasive manner as well as through amniocentesis, which is tan invasive study based on obtaining amniotic fluid with a syringe through the abdominal wall.
Both DNA examination methods can either 100% exclude or confirm Down syndrome in the fetus. Genetic tests performed on the mother’s blood, such as NIFTY and Harmony will cost about 2,500 PLN (they are not reimbursed by the NHF).Amniocentesis is refundable only if there are medical indications for it. To get a referral, the expectant mother must report to the genetic clinic. This study should be performed between the 15th and 18th week of pregnancy – conducted earlier may be less reliable.