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Genetics prenatal diagnostic service


Prenatal Referrals

To make a referral please call the duty clinician on 020 7188 1364 to discuss the referral, then email the urgent referral form to Include details of the affected individual and their relationship to your patient. We can offer patients who need an urgent referral an appointment within one week.

Patients are usually seen within a few days of referral.

The consultant geneticists and genetic counsellors work closely with the Fetal medicine unit (FMU) , fetal cardiology and paediatric services within Guy’s and St Thomas’ Hospital to offer comprehensive care for our patients.

This specialised service offers those at risk of having pregnancies or children with genetic conditions options for testing in pregnancy. Some pregnancies are found to have complications when abnormalities are identified on a scan. The expertise of the prenatal and clinical genetics teams give patients access to the best advice and the opportunity of talking through the diagnostic and treatment options available to them.

Joint clinics are held every week in fetal medicine and clinical genetics. A multidisciplinary meeting is held each week to discuss ongoing clinical cases.

Updated Prenatal Array CGH Service

From the 4th of September 2017 we will be offering an updated prenatal array CGH service with higher resolution analysis. This change in practice is to align ourselves with the ‘Recommendations for the use of chromosome microarray in pregnancy’ from the Royal College of Pathologists (June 2015 version 1) that recommend the use of a microarray platform with a minimum resolution of ~400 kb across the genome.

This change in testing will mean that the following results may now be reported:

  •  “Abnormal result” - this is a significant result which explains the ultrasound scan findings.
  • Chromosome imbalance detected” – this means that a chromosomal change has been found that may be significant. This may also be found in people without problems.
  • No clinically significant imbalance detected” - this means the test did not show a genetic change that explains the ultrasound scan findings. Please note, it does not mean that there is no genetic anomaly as there could still be a single gene or chromosomal change that the array CGH has not detected or has not been reported as per national guidelines.
  • Incidental findings, such as increased risk of cancer later on in life will also be reported; this chromosome change may or may not have been inherited from a healthy parent. Carriers of these types of chromosome changes could benefit from screening to detect cancer earlier and improve the success of treatment.

We have designed an information leaflet  entitled “Prenatal Array CGH” to explain our new service and a consent form for all patients to read and sign as part of consenting for invasive prenatal testing where array CGH is indicated. Each FMU department undertaking testing should use both the leaflet and the consent form. The signed consent forms should be kept with the patient notes within the FMU department. Please do not send consent forms to the Genetics Laboratory.

To help with interpretation of results from the higher resolution analysis, we will require a copy of the most recent ultrasound scan to be sent to the Genetics Laboratory with the sample and request form. If the scan results are not included, this coulddelay the prenatal array CGH test. In addition, and in line with the Royal College of Pathologist Recommendations, the cut-off for a referral of isolated nuchal translucency to be eligible for array CGH will be ≥3.5 mm from the 4th September.

Staff involved

  • Dr Muriel Holder, consultant geneticist
  • All of the genetic counsellor team