Combined Test (11+0 to 13+6 weeks)
The standard and proven method to screen for fetal chromosomal abnormalities (like trisomy 21 - Down Syndrome) and for severe fetal anomalies. This examination requires special training as well as annual audits of the screening performance of the examiner (Fetal Medicine Foundation certification).
This screening method combines information from a detailed ultrasound scan and from the evaluation of a maternal blood sample. It can identify about 93% of all fetuses with trisomy 21 and gives a false positive result in about 2-3% of cases. The great advantage of Combined Test over other non invasive screening methods is the very detailed ultrasound examination of the fetal anatomy. This can pick up the majority of fetal structural problems as well as most of the major cardiac defects as early as 11-14 weeks.
Another merit of this examination is that it can be easily combined with a screening test for preeclampsia (one of the most common and severe pregnancy complications). In the case of a screen positive result for preeclampsia a prophylactic treatment can bring the risk down close to normal levels again.
Combined Test (together with Screening for Preeclampsia) is best performed as the first step in the screening for fetal anomalies and for pregnancy complications.
This screening was developed and is supervised worldwide by the Fetal Medicine Foundation in London (for more information please see: www.fetalmedicine.org).
Screening vs Diagnostic test: