精子注入法は安全だ　

2000/3/27

生殖技術は奇形の赤ちゃんが産まれる率が高くなる原因にはならない、と技術者は言う。1つの精子を選び直接卵に注入して受精させる、ICSI(卵細胞質精子注入法）は欠陥のある赤ちゃんをつくると心配されている。ICSIによって生まれた1000人以上の赤ちゃんの調査によると奇形児の率がとても高いことがわかった。しかしこれは他の原因によるものがほとんどで、体外受精による多胎の誕生や早産と同じぐらいの率である。

A fertility technique is not to blame for the birth of higher numbers of malformed babies, experts say.
There have been fears, supported by controversial research, that intracytoplasmic sperm injection (ICSI) could lead to birth defects.
The treatment involves selecting a single sperm and injecting it directly into the egg to fertilise it.
But a study of more than 1,000 babies born following ICSI treatment found that that while the rate of malformed children was much higher, this was mostly due to other reasons, such as the higher number of multiple births, or premature babies following IVF.
The researchers from Sweden, who published their work in the journal "Human Reproduction", did however find one malformality which might be due to ICSI.
The number of hypospadias - a deformity of the penis - was more than expected after ICSI.
Doctors believe that because ICSI is usually used to help men with fertility problems, then their genetic defects could be being passed on.
Dr Ulla Britt Wennerholm, from Goteborg's Sahlgrenska University Hospital, who led the study, said: "About 20,000 babies have been born worldwide through ICSI in the last decade and the vast majority of these are normal, healthy children."
She added: "We know that hypospadias appears to be particularly associated with paternal fertility problems so a link directly with ICSI is plausible."
Scientists put forward a number of reasons why babies born through ICSI could be at risk.
Single sperm
Normally, a man produces millions of sperm in a single ejaculation, so only those with better qualities will have a chance of fertilising the egg.
In ICSI, a single sperm is chosen and injected - the genetic material it contains may not be the same as a sperm that would normally succeed naturally.
In addition, doctors feared that there might be damage to the egg by the injection technique itself, or by the chemicals used during the process.
And the fact that genetic material from a man who would not normally be able to reproduce is being passed on to a child also could carry a risk of other genetic defects.
Dr Alastair Sutcliffe, a lecturer in child health from University College London, said: "There is no natural selection involved in ICSI - only one sperm is selected.
"One paper suggested a doubled risk of malformities, and there is anecdotal evidence, but nobody has carried out a study of this size before."
The Swedish result means that most of these fears have been eased.
The risks of IVF remain the fact that it often results in twins or even triplets, which are frequently born prematurely.