HAEMOPHILIA GENE CARRIER - Fact Sheet 2

Fact sheet 2: Pregnancy - screening tests and other procedures

• Thinking about becoming a parent?
  This fact sheet is intended for women who know they carry the haemophilia gene and who maybe thinking about planning a family. Medical technology offers a variety of screening and testing possibilities, which open up a number of options for women who are carriers. This fact sheet has been written to explain theses options.
  
  
• Inheritance of Haemophilia
  Women who carry the haemophilia gene may pass the gene on to their children. They have a 1 in 4 chance of having a boy baby with haemophilia. This is the same as saying that for every boy baby, there is a 1 in 2 chance of that baby having haemophilia and for every girl baby, there is a 1 in 2 chance of that baby inheriting the carrier gene. Daughters of fathers with haemophilia will automatically become haemophilia carriers.

 

• What are the options available to me?
  1. Some women have no real worries about the possibility of having a child with haemophilia.
  2. For some women having a child with haemophilia is not for them and they may wish to plan their family using medical techniques to prevent the birth of a child with haemophilia.
  3. Some women feel unsure, but would like to know if the child they are carrying has haemophilia.

Whatever you decide it is important that your factor levels are monitored throughout your pregnancy.

• What medical techniques are available?
  There are a number of tests available for carrier women who become pregnant. These tests fall into two categories:

1. Tests to determine sex of the foetus: Ultrasound

2. Tests to determine haemophilia status of the foetus: Chorionic Villus Sampling (CVS).

If you have low levels of factor VIII or IX you will need to discuss with your doctor whether you will need clotting factor replacement treatment before these procedures to avoid extra bleeding risks.

Chorionic Villus Sampling (CVS) - CVS involves testing a small amount of tissue (chorionic villi) from the placenta. The placenta is on the wall of the uterus. The developing foetus is attached to it by the umbilical cord. The placenta is involved in hormone production of the developing baby.

Abdominal CVS - Under ultrasound the placental tissue is located. The chorionic villi sample is obtained by passing a fine needle through the abdominal wall and into the placenta using ultrasound for guidance. A local anaesthetic is usually given to numb the area where the needle is passed prior to the procedure. The chorionic villi is removed through the abdomen. This procedure is carried out during weeks 11 - 13 of pregnancy.

If the doctor is unable to obtain enough tissue or if the laboratory is unable to make an analysis of the tissue, more than one CVS is necessary to make a diagnosis. This happens only very occasionally.

A CVS is done as an outpatient test. There is no need to fast before the test. You will need to have a comfortably full bladder for the uterus to be in the best position for the ultrasound.

The results are usually available in 1-3 weeks.

Vaginal CVS - On very rare occasions a vaginal approach to CVS may be required (under what circumstances??) This is very similar to a cervical smear test. While the ultrasound is being used on the abdomen to locate the baby in the uterus, a speculum is inserted into the vagina to widen the opening of the vagina so that the cervix can be seen clearly.

A fine tube is then passed through the cervix into the uterus. The image of the tube can be seen clearly in the ultrasound picture and so can be guided to the placenta. A small sample of chorionic villi is removed. This procedure is carried out during weeks 11 - 13 of pregnancy.

• What are the risks? Studies have shown that the miscarriage rate related to the test is less than 1% above the underlying risk of miscarriage (1 in 100 pregnancies). A miscarriage related to the procedure will usually occur within a short time following the test.

Some women experience cramping and occasionally, some vaginal bleeding after CVS. These symptoms are normal and should only last a day or so. Contact your doctor if you have any concerns.

• Ultrasound - An ultrasound can be performed to determine the sex of the foetus at 18 - 22
  weeks of pregnancy. This test is now over 95% accurate so if it suggests that the foetus is female, some women may decide not to consider other more invasive tests. It will be important for your delivery team to know the sex of your baby, as precautions may need to be taken during the birth.
  
  
• What are my options if the test is positive for haemophilia?
  If the test proves that haemophilia is present you may chose to continue the pregnancy without further intervention or you may decide to terminate your pregnancy.

Whatever decision you make, it is a very personal choice for you and your family although advice and information from a health professional or other expert advisor may help e.g. British Pregnancy Advisory Service.

• Are there any other options?
  Some women chose not to have children. Others pursue other ways of having a child such as adoption or fostering. Your local authority will be able to advise you on certain aspects of this and there are a number of private agencies that also facilitate fostering and adoption procedures. If you are considering this take advice from professionals.
• Assisted conception to eliminate the chance of having a child with haemophilia:
  This is an experimental technique known as pre-implantation genetic diagnosis (PGD), which is done in combination with in-vitro fertilisation (IVF). This medical technique is only available at very few fertility centres throughout the UK and is difficult to access. The current 'success' rate (live births after PGD and IVF) is around 21%. This procedure is not free. Costs vary between different IVF units. Some health authorities may consider paying this, however, this is very unlikely. The cost of a private treatment is normally around £3,000 plus the cost of drugs.

A fact sheet is available on Pre-implantation Genetic Diagnosis. (see reading list below)

Useful contacts:

British Pregnancy Advisory Service Austy Manor Wootton Wawen Solihull West Midlands B95 6BX Helpline: 08457 304030

The Family Planning Association(FPA) 2 - 12 Pentonville Rd London N1 9FP Tel: 0207 837 5432 Helpline: 0207 837 4044

Reading List
· Introduction to Haemophilia and Related Bleeding Disorders

· Inheritance of Haemophilia - National Haemophilia Foundation

· On Being a Carrier… - Haemophilia Foundation Australia

· Raising a Child with Haemophilia. A Practical Guide for Parents. - Laureen Kelley

· Living with Haemophilia - Peter Jones

(These publications are available from the UK Haemophilia Society).

Acknowledgements
We are grateful for the help and advice given in the production of this factsheet. In particular we would like to thank Debra Pollard and Chris Harrington, haemophilia nurse specialists, The Royal Free Hospital, Dr Paul Giangrande, Haemophilia centre director at Churchill Hospital, Oxford and Dr Stuart Lavery, Fellow in Reproductive Medicine at the Hammersmith Hospital.

We would also like to thank the Haemophilia Foundation Australia for allowing reproduction of some of their material in the writing of this factsheet.

The Lincoln and District Group, a local group of the Haemophilia Society, have sponsored this and other factsheets. We would like to acknowledge their vital contribution to the work of the Haemophilia Society.

This factsheet can be reproduced in a larger print. Please contact the Haemophilia Society for details.

If you would like to comment on this or any of the Society's fact sheets contact a member of the services team on 0800 018 6068 or email: info@haemophilia.org.uk

The factsheet can only give basic general information drawing on medical opinion and evidence available at the time of writing. Different people may give you different advice on certain issues and there may be some variations in the way care is managed in different hospitals and in different areas. It is important that you contact your own doctor(s) and nurses(s) for further information and advice on your own individual circumstances.

Published June 2001
Revised April 2003
Revised June 2003