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The following paper was given at our conference by Linda Willis.
Genetic Counsellor. St Mary's Hospital. Manchester.
Linda's paper was entitled 'Prenatal Options'.
The objectives of prenatal diagnosis is to
1 Allow choice.
2 To provide reassurance.
3 Maximise options.
4 Prepare parents.
Issues in Prenatal testing for VHL.
What is the aim?
How would it benefit you?
What would you do with the information?
Would you continue with the pregnancy?
What are the psychological aspects?
What are the health implications?
What are the alternatives? e.g. screening in childhood
Prenatal diagnosis in VHL.
In 95%of cases of VHL where a mutation is found the options are
Chorionic villus sampling (CVS) at 11weeks gestation
Amniocentesis at 16 weeks gestation.
Preimplantation genetic diagnosis.
CVS. An invasive test done under scan control.
Results available in 1-3 weeks.
Miscarriage risk associated with the procedure 1%.
Usual risk of miscarriage at this gestation 2-3%.
Amniocentesis.
Invasive test at 16 weeks gestation under scan control.
Results available in 10-14 working days.
Miscarriage risk 1-300 now quoted at St.Mary's.
Preimplatation genetic diagnosis.
A diagnostic service.
Specialised treatment.
Uses assisted conception.
Has limitations and risks.
An alternative to prenatal diagnosis and termation of pregancy.
Usually fertile couples, and can be their preferred option.
Should have had genetic counselling.
PGD IS CHALLENGING.
Technically, emotionally, physically, psychologically and financially.
Where is it done.
Guy's and St.Thomas's Hospital. London.
University College Hospital. London.
Care in the Park Hospital. Nottingham. (private)
London Bridge Hospital.
How much does it cost?
£6550 per procedure inclusive of drugs.
6 consultations.
Expenses incurred in attending hospitals.
? P.C.T. funding
PGD must be done in HFEA licenced hospitals.
Accessing PGD.
Combined referral to assisted conception unit and genetics.
Team discussions of feasability of offering PGD.
Issues for discussion.
Previous history, other options, why PGD, blood tests and semen analysis, funding, and the possibility of misdiagnosis.
Success of PGD.
Success rate is low.
Depends on the number of transferred embryos
Age of woman, success rate diminishes with increased maternal age, no successful pregancies at 40+.
Success rate at start of cycle-20% or 1:5
Increases to 30-35% if embryo in transferred.
If apositive pregnancy test, there are still some risks: 30% miscarriage risk and 2% of an ectopic pregnancy.
Fertilisation.
Ovarian stimulation and its associated risks.
Egg collection
Fertilisation in the laboratory.
Cell biopsy (day 5)
Diagnosis within 24 hours.
Option of prenatal tests
Paediatric follow up of the baby.
Outcome of testing.
Affected embryo
Unaffected embryo.
Failed test.
Results are not 100% accurate, but the misdiagnosis at Guy's is1%.
PGD in VHL
In the early stages, only available since December 2007.
Some couples have been seen for initial consultations.
So far no cases have reached the PGD. stage.
Results of PGD for all conditions at Guy's Sept. 1997-Jan 2008.
585 cycles of PGD to date.
472 have achieved egg collection
398 (68%) have proceeded to embryo transfer.
139 clinical pregnancies
130 babies born
20 ongoing pregnancies.
Linda said that T.I.M.E. was essential in considering PGD. for VHL.
Time to talk and discuss all the many facets of the procedure.
Information to be given and its implications understood.
Management by genetic and assisted reproduction units outlined.
Explanations throughout all the processes need to be given.
Linda's talk provoked much interest and discussion and we are grateful to her for her time in preparing her paper, and attending our conference.
If you would like a copy of Linda's paper please contact me by e-mail maryweetman@waitrose.com or by phone on 01204 886112.
Other information id available from:
Ms. Alison Lashwood.
Clinical Genetic Department.
7th. Floor. New Guy's House.
Guy's Hospital.
LONDON. SE1 9RT.
Tel. 020 188 1364.
www.guysandstthomas.nhs.uk/genetics.
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