The baby, due next month, will be born unaffected by mucolipidosis — a rare inherited metabolic disorder where growth usually stops before a child reaches the age of two. Most people born with mucolipidosis do not survive past early childhood.
The couple already have two children, one of whom is healthy and one severely affected by the disorder.
The parents are both carriers of a mutation affecting the mucolipidosis gene and, without pre-implantation genetic diagnosis (PGD), had a one-in-four chance of having a baby affected by the condition, according to Dr John Waterstone, medical director of the Cork Fertility Centre, where the couple are being treated.
He said the pregnancy is the first reported incidence in the world of successful PGD, with karyomapping in the case of mucolipidosis.
PGD involves screening embryos before they are implanted in the uterus, allowing the safe transfer of those identified as unaffected by the condition a couple was in danger of passing on.
Until recently, PGD tests for disorders caused by inheritance of a defective gene had to be tailor-made for each couple, which Dr Waterstone said were costly and took months.
Karyomapping — carried out on the centre’s behalf by Reprogenetics UK — provides a test for PGD of almost any known gene defect with a rapid turnaround time. Dr Waterstone said it was “more powerful, more accurate, quicker (two week turnaround time), and not more expensive”.
He said six couples at the clinic had been through the process. One couple had already given birth to a baby without cystic fibrosis, despite the parents being affected.
Of the remaining five, three are pregnant, including the couple of the baby screened for mucolipidosis. The treatment costs €9,500 to €12,000.
PGD is only available at the Cork Fertility Centre to people at risk of passing on certain life-limiting and debilitating conditions, such as CF and muscular dystrophy.