Prenatal – Abnormal Ultrasound Scan Findings

Introduction

The NHS fetal anomaly screening programme (FASP) provides screening for fetal anomalies to all pregnant women in the UK. This includes an ultrasound scan as part of the Combined test between 10 and 14 weeks gestation, measuring fetal nuchal translucency, and a fetal anomaly scan between 18 and 20 weeks gestation. Where nuchal translucency measurements are above 3.5mm in the first trimester or 6mm in the second trimester or other fetal structural or growth abnormalities are identified by scan, women are offered an invasive prenatal diagnostic test. This laboratory will carry out an initial rapid Quantitative Fluorescent PCR (QF-PCR) test on the sample to exclude trisomy 13, 18 and 21 (Patau, Edwards and Down syndromes respectively), triploidy, and Turner syndrome where there is a raised nuchal translucency or other clinical indication. G-banded chromosome analysis is performed where aneuploidy is identified to confirm the finding and give an indication of the risk of recurrence in future pregnancies. Samples that show a normal result by QF-PCR will be tested by microarray analysis to look for genomic imbalances that may explain the cause of fetal abnormalities. Testing may be performed on either chorionic villi (between 11 and 14 weeks gestation) or amniotic fluid (after 15 weeks gestation). QF-PCR results will usually be available via the antenatal clinic within three days and microarray or chromosome analysis results within fourteen calendar days.

Referral information

We accept prenatal referrals (chorionic villus and amniotic fluid samples) from pregnant women where ultrasound scanning has identified a nuchal translucency measurement of greater than 3mm in the first trimester or 6mm in the second trimester, there is intrauterine growth restriction without placental insufficiency or the scan has identified one or more fetal structural abnormalities. Samples from women with a known family history of a chromosome rearrangement will be tested by microarray or G-banded chromosome analysis, depending on the rearrangement.

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 *
QF-PCR POA 3 cd
Prenatal microarray or chromosome analysis POA 14 cd

Test validation & quality assurance - information for users

The QF-PCR test is for trisomy 13, 18, 21, triploidy, and Turner syndrome (where indicated) 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. Microarray analysis will not detected balanced rearrangements and may not detect mosaicism. Maternal cell contamination is excluded prior to testing by analysis of a maternal blood sample. Where the sample size is insufficient for microarray testing on uncultured material, the sample will be cultured and testing performed on cultured cells. In some cases, microarray analysis may identify incidental findings unrelated to the primary reason for referral.  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 plus 4ml EDTA maternal blood sample

Referral guidelines

Please see our referral guidelines for more information.

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