- Reference Number: HEY1022/2024
- Departments: Maternity Services
- Last Updated: 31 January 2024
Introduction
This leaflet has been produced to give you general information about the prenatal array CGH test. Most of your questions should be answered by this leaflet. It is not intended to replace the discussion between you and your doctor/midwife, but may act as a starting point for discussion. If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team caring for you.
What is Prenatal Array CGH?
Prenatal array CGH (comparative genomic hybridisation) is a test used to pick up chromosome changes which are too small to be seen by the standard tests available in pregnancy.
What are chromosomes?
Chromosomes are structures which carry genes, and genes are instructions to tell the body how to develop and function. In each cell of our body we have 23 pairs of chromosomes. These are numbered 1 to 22 with the final pair being the sex chromosomes (XX for a girl, XY for a boy). We inherit one chromosome from each parent. Having too much or too little chromosomal material can cause significant problems in development. For instance three copies of chromosome number 21 causes Down syndrome.
Why has array CGH been offered to you?
Ultrasound scans have shown that your baby has an increased chance of having too much or too little chromosomal material. Array CGH is used to see if the baby has a chromosome change which may explain the ultrasound findings.
What are the advantages of Array CGH?
The main advantage of array CGH is that it can detect very small chromosome changes which cannot be seen by the standard chromosome test. A change in the chromosomes may explain the ultrasound findings and allow more precise information to be given about what this means for your baby.
What are the disadvantages and limitations of array CGH?
Array CGH does not detect all genetic changes. A normal result does not exclude a genetic condition in your baby. Sometimes results can be difficult to interpret and a blood sample from both parents might help to interpret the result.
Are all chromosome changes reported?
Some chromosome results have unclear meaning for the health of your baby. These include:
- Changes where there is not enough information available to tell the health professionals if it will cause a problem for your baby.
- Changes that give an increased chance of medical and/or learning problems, but the exact risks are uncertain.
Due to this uncertainty it has been agreed by national experts that some of these changes will not be reported.
Why do some people choose not to have the array CGH?
Array CGH may identify a chromosome change which is not related to the ultrasound findings. It may have implications for the future health of your baby and possibly for other family members. For example, it may show your baby will have an increased risk of cancer later on in life. Some people don’t want to know about these types of chromosome changes.
What happens next?
The first part of the test looks at chromosomes 13, 18 and 21 as these are the most common chromosomes to be associated with ultrasound scan changes. If this test is normal the array CGH test will be done. The result will be available in about 3 weeks. Your Health Professional will contact you when it is available. Occasionally for technical reasons the array CGH is not possible.
If significant chromosome changes are identified you may be offered an appointment with a member of the genetics team to discuss the result.
Should you require any further advice on the issues contained in this leaflet, please do not hesitate to contact the Antenatal screening midwives on tel: 01482 382737.
General Advice and Consent
Most of your questions should have been answered by this leaflet, but remember that this is only a starting point for discussion with the healthcare team.
Consent to treatment
Before any doctor, nurse or therapist examines or treats your child, they must seek your consent or permission. In order to make a decision, you need to have information from health professionals about the treatment or investigation which is being offered to your child. You should always ask them more questions if you do not understand or if you want more information.
The information you receive should be about your child’s condition, the alternatives available for your child, and whether it carries risks as well as the benefits. What is important is that your consent is genuine or valid. That means:
- you must be able to give your consent
- you must be given enough information to enable you to make a decision
- you must be acting under your own free will and not under the strong influence of another person
Information about your child
We collect and use your child’s information to provide your child with care and treatment. As part of your child’s care, information about your child will be shared between members of a healthcare team, some of whom you may not meet. Your child’s information may also be used to help train staff, to check the quality of our care, to manage and plan the health service, and to help with research. Wherever possible we use anonymous data.
We may pass on relevant information to other health organisations that provide your child with care. All information is treated as strictly confidential and is not given to anyone who does not need it. If you have any concerns please ask your child’s doctor, or the person caring for your child.
Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about your child. For further information visit the following page: Confidential Information about You.
If you need information about your child’s (or a child you care for) health and wellbeing and their care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.
