Lab Blind
Study suggests test tube babies are seven times more likely to develop retinoblasma
By Richard Ingham,
Agence France Presse
PARIS
Test tube babies may be vulnerable to eye cancer, Dutch doctors warn in the third study in as many months to suggest that children born to in vitro fertilization (IVF) run serious health risks.
Researchers led by Annette Molle, an ophthalmologist at Amsterdam's Free University Medical Center, say that in less than 16 months, they detected five cases of retinal tumors among children conceived through IVF.
Between 1.0 and 1.5 percent of children born in the Netherlands are conceived through IVF, says Molle's team. That means, statistically, IVF children are up to seven times likelier to develop retinoblastoma than counterparts born through natural conception.
The doctors, whose work is published in The Lancet, say they are worried. They say it is urgent to see if these cases are more than just a freakish cluster and if there is an underlying cause.
In three of the patients, the cancer had affected one eyeball, and the tumor was successfully removed. Two of the children had tumors in both eyeballs. In one case, surgeons had to remove one of the eyes, but successfully treated the other with radiotherapy. In the other, radiotherapy saved both eyes.
Likely Causes
Dr. Molle speculates that there could be several causes. One is that the same genes that caused infertility in one or both of the parents could also have some hitherto unknown link with retinal cancer.
Another theory is that the retinoblastoma was somehow caused by the powerful drugs taken by the children's mothers to induce ovulation.
There may also have been a change in the IVF procedure, such as a change in the chemical culture in which the fertilized egg is bathed to promote cell division, she suggests.
IVF began in the Netherlands in 1980, and there were no known cases of retinoblastoma among IVF children until this batch, born between 1997 and 2001.
The research is the latest in a series of studies that, despite their limitations, are assailing the faith in IVF as a technique that does not result in any higher rate of defects than natural conception.
A US and a British study perceived a link between IVF and Beckwith Wiedemann syndrome, a rare condition that causes excessive growth, low blood sugar, defects in the abdominal wall and kidney abnormalities.
Children born from IVF or intracytoplasmic injection, in which sperm is directly injected in the egg, were up to six times likelier to contract this disease than the general population, the studies found.
Beckwith Wiedemann syndrome is linked to malfunctioning genes located on Chromosome 11. The scientists suspect that IVF disrupts "imprinting," a process that occurs at the earliest stages of conception.
An embryo is a combination of a set of genes from its mother and a set of genes from its father. Under imprinting, the activity of specific genes, from either the paternal or the maternal side, is muted during fetal development. This way, there is no clash of competing genes, and the embryo develops normally.
"The genes themselves are not necessarily any different but imprinting controls how active the gene is," said Wolf Reik, a University of Cambridge scientist. "If the imprinting goes wrong, control is lost and this can result in unregulated growth."
Meanwhile, a Swedish study published February last year found that IVF children run a three times higher risk of cerebral palsy damage to the brain that hampers motor skills, speech and memory.
That problem may not lie with IVF conception itself but the practice of implanting several fetuses at the same time in the hope that at least one will stick to the side of the uterus and lead to a live birth.
Multiple pregnancies have a record of low birth weight, premature birth, and retarded development.
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