補助的生殖技術は児の発育に影響するか　

1998/5/23ロイター　　いままで体外受精や顕微授精の安全性についてその安全性をチェックする組織が存在しなかった。今回発表された２つの施設の調査結果によると、オーストラリアのグループは出生した児の奇形率に差はないが、知能の発達や１年目の発育が遅れるかもしれないという。一方ベルギーのグループはそれを認めていない。しかし、いままで児に対する安全性が調べられずに補助的生殖技術が導入されてきたことより、将来は科学者や政府組織による安全性のチェックが必要であろう。

Assisted reproduction may affect development

NEW YORK (Reuters) -- The results of two studies published in the May 23rd issue of The Lancet open debate over the safety of assisted reproductive techniques with respect to infant and early child development.

Unlike drugs, new assisted reproductive techniques aren't subjected to clinical scrutiny by government agencies such as the US Food and Drug Administration. There are no regulations requiring animal testing or long-term safety monitoring before an assisted reproductive technique is offered routinely to infertile couples.

One such technique is intracytoplasmic sperm injection (ICSI), in which a single sperm is injected into an oocyte (egg). A potential drawback of this technique, a team of editorialists explain in The Lancet, is that it circumvents "the selective barriers developed during evolution."

But since the introduction of ICSI in treating infertility, experts writing in The Lancet estimate that tens of thousands of children have been born as a result of the procedure. And the two studies published Saturday are the first to compare the development of these children with that of children conceived naturally.

In one study, Dr. Jennifer R. Bowen of the Royal North Shore Hospital in St. Leonards, Australia, and a multicenter team compared the developmental outcomes at age 1 year of 89 children conceived by ICSI, 84 conceived by routine in vitro fertilization (IVF), and 80 conceived naturally.

Although the incidence of birth defects or major health problems was similar in the three groups, the Australian team found that children conceived by ICSI scored significantly lower on a mental development index compared with children conceived either by IVF or naturally. In addition, a significantly higher proportion (17%) of ICSI children demonstrated mild developmental delays at 1 year compared with IVF children (2%) and naturally conceived children (1%). All three groups appeared to respond similarly to tests of motor performance.

"Although mild developmental delay at 1 year is not always strongly predictive of later intellectual impairment, tests that assess cognitive or mental skills are generally felt to be more predictive of long-term outcome than tests that assess motor skills," Bowen and colleagues explain. In this light, the findings raise "...concerns regarding the developmental potential of children conceived by ICSI compared with IVF and naturally conceived children," and "...support the need for developmental follow-up of children conceived by ICSI."

But elsewhere in the journal, Dr. M. Bonduelle and colleagues at Brussels Free University in Belgium report that in their own study, they found "...no indication that ICSI children have a slower mental development than the general population." The Belgian investigators compared scores on a scale of mental development at 2 years of age in 201 children conceived by ICSI and 131 conceived by IVF.

Although the results for these two groups of children were "...no lower than (those) for the general population," Bonduelle and others point out that further studies "...taking into account parental background (are) needed to be able to draw final conclusions."

In a related editorial, Dr. E.R. te Velde of University Hospital in Utrecht, the Netherlands, and others point out that the findings in these two studies "...carry a serious warning." They explain that the introduction of assisted reproduction techniques into routine use should follow strict clinical assessment and monitoring guidelines, similar to those used to examine the safety and efficacy of drugs, and that the development of such regulations should include both scientists and governments.

According to the editorialists, "Lessons learnt from the unexpected effects on fetal development of drugs that were not adequately assessed before introduction should apply here." SOURCE: The Lancet 1998;351:1524-1525, 1529-1534, 1553.