How genetic screening can reduce risk of cystic fibrosis

Genetic testing of an embryo prior to implantation gives people with genetic diseases the chance to become parents without passing on inherited conditions

Patrick Mullane and Dr John Waterstone with baby Bridget. Photograph: Micheal McSweeney/Provision

Patrick Mullane and Dr John Waterstone with baby Bridget. Photograph: Micheal McSweeney/Provision

 

All babies are special but baby Bridget Mullane is particularly precious as her parents thought they might never be able to have a family together. They are at high risk of having a baby born with cystic fibrosis (CF), a disease that primarily affects the lungs and the digestive system.

Bridget’s birth this year following a technique used to screen embryos for genetic conditions such as CF was hailed as a major milestone for Irish reproductive medicine.

Her father, Patrick Mullane, who is 34, has CF, the most common genetic disease in Ireland, while her mother, Lisa Cooke, who is 24, discovered she was a carrier of the CF gene after being tested. The couple, from Dromahane near Mallow, Co Cork, were facing the possibility that they would never be able to have children together when they heard about Pre-implantation Genetic Diagnosis (PGD) which had just been introduced to Ireland.

PGD is a technology that allows genetic testing of an embryo prior to implantation. Conception takes place through IVF and only the embryos diagnosed as being free of a specific genetic disorder are transferred into a woman.

The treatment is suitable for couples who are at risk of transmitting an inherited genetic disease to their children such as CF, Batten disease, muscular dystrophy, Fragile X or Fanconi Anaemia.

Prior to the development of the PGD technology, the only option for such couples was either to avoid becoming pregnant, or to become pregnant and undergo chorionic villus sampling or CVS (which involves taking a sample of cells from the mother’s placenta) at 11 weeks, or amniocentesis (which involves taking a small amount of amniotic fluid from around the baby) at about 14 weeks. If the foetus was affected by a life-threatening, inherited disease, the couple faced the awful decision of whether to continue with the pregnancy.

After her first round of PGD at Cork Fertility Clinic, Cooke discovered she was pregnant and the couple were thrilled when their little daughter was born weighing a healthy 7lbs 9oz (3.4kg) at Cork University Maternity Hospital on June 27th. Bridget was tested for CF at birth and was found to be a carrier of the gene.

“We realise how lucky we were to get pregnant on the first attempt. I was nervous at the start but the treatment wasn’t as bad as I thought it would be. I was told to do a pregnancy test two weeks after the embryo was transferred into me, and I was actually on a train in London when I found out I was pregnant,” she says.

Genetic counselling

The couple are already talking about having a second baby, and they are planning to use some of the other embryos that are in storage at the fertility clinic. Mullane is optimistic about the future.

“I lead a fairly normal life. I go to the gym to keep myself healthy. Staying fit helps to keep my lungs clear. I’m on a mild antibiotic all the time and I take tablets to help with my digestion. There’s a new drug for my mutation of the disease in stage 3 trials so hopefully that will become available some time soon.”

Ireland has the highest incidence of CF in the world with about one in 19 Irish people said to carry one copy of the defective gene that causes it. Many people with the disease in Ireland can now expect to live into their 30s, 40s and beyond; a 76-year-old woman recently became the oldest woman in the country to be diagnosed with CF.

High price

Alicia May of CF Ireland agrees that the treatment should be funded by the HSE, saying that infertility should be treated like any other secondary complication of CF such as diabetes or osteoporosis. The organisation is currently drafting a policy document to advocate for the State funding of fertility treatment in CF.

“Our fertility grant has been operating for a few years, it is hugely beneficial and hugely valued by people with CF, and we have had quite a few success stories. We have not had to turn anybody down yet, but there is more demand for the scheme with people living longer and wanting to start families, which would not have been possible in the past.

“Unfortunately, PGD is so expensive that it excludes many people with CF who cannot work and are dependent on disability allowance.”

Dr John Waterstone, medical director of the Cork Fertility Centre and a consultant obstetrician at Cork University Maternity Hospital, stresses that PGD is not an easy process and is “not for everybody”.

He says that Cooke was a very favourable candidate for the treatment due to her age and the large quantity of good-quality eggs she produced. “This is not an easy process and we have to be very sensible about who we offer it to. IVF is more successful for younger couples and PGD is a form of IVF. Some of the embryos are not going to be usable because of the genetic condition involved, and in older women, there will be fewer eggs to start with.

“If a woman is older and less likely to produce a lot of eggs, it is less likely that the treatment will take, so unfortunately she would not be a good candidate and we would not offer her this treatment. Obviously, when it does work, it’s fantastic and is the neatest solution to the problem of couples at risk of passing on a genetic condition.”

The Cork centre has a number of couples going through PGD at the moment and one other couple with a rare genetic disorder are expecting a baby. The treatment is also being offered by Beacon Care Fertility in Dublin, part of the Care chain in the UK, where some 23 couples have been through PGD to date but there have been no successful pregnancies yet.

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