Prenatal – Increased Risk of Down, Edward or Patau Syndrome Following Screening


The NHS fetal anomaly screening programme (FASP) provides screening for fetal anomalies as well as Down, Edwards and Patau syndromes to all pregnant women in the UK. Women are offered the Combined test between 10 and 14 weeks gestation which measures fetal nuchal translucency by ultrasound scan and pregnancy associated proteins in maternal blood serum. Patients presenting later in pregnancy are offered the Quadruple test measuring maternal serum only. The screening test gives a risk of the pregnancy being affected with Down, Edwards or Patau syndromes. Where this risk is high (greater than 1 in 150), an invasive prenatal diagnostic test is offered. This involves either chorionic villus sampling (between 11 and 14 weeks gestation) or an amniocentesis (after 15 weeks gestation). This laboratory will carry out a rapid Quantitative Fluorescent PCR (QF-PCR) test on the sample to diagnose or exclude trisomy 13, 18 and 21 (Patau, Edwards and Down syndrome respectively). Results will usually be available via the antenatal clinic within three working days. Chromosome analysis is performed where trisomy is identified to confirm the finding and give an indication of the risk of recurrence in future pregnancies.

Referral information

We accept prenatal referrals (chorionic villus and amniotic fluid samples) from pregnant women with a high risk of trisomy 13, 18 or 21 (Patau, Edwards and Down syndromes respectively), either following antenatal screening, a previous aneuploid pregnancy or due to a known familial chromosome rearrangement predisposing to trisomy 13, 18 or 21.

Price & reporting times

NHS referrals to this service are paid for where there is an existing specialist commissioning contract for genetic testing. In other cases please contact the lab for prices.

Test Price (£ ex VAT) TRT *
Prenatal chromosome analysis POA 14 cd
QF-PCR (chorionic villi) POA 3 cd
QF-PCR (amniotic fluid) POA 3 cd

Test validation & quality assurance - information for users

The test is for trisomy 13, 18 and 21 only and will not detect mosaicism or structural rearrangements. Rarely, testing may be uninformative or fail to give a result either due to maternal cell contamination or other factors. Maternal and paternal blood samples may be requested to help interpret results. Where trisomy is identified or the test is uninformative, G-banded chromosome analysis will be performed if the sample size is sufficient. This laboratory participates in the CEQAS quality assessment scheme for this test.

Sample requirements

Amniotic fluid (minimum 15ml)/chorionic villus biopsy (CVB) (minimum 10mg) sample

Maternal carriers of balanced rearrangements: 2-5ml blood in EDTA

Referral guidelines

Please see our referral guidelines for more information.