Study Finds Fertility Treatment Not Linked to Most Birth Defects

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March 29, 2000 (New York) -- A study of a fertility treatment called intracytoplasmic sperm injection (ICSI) has found that babies conceived through the method are more likely to have a defect of the urethra known as hypospadias. But other abnormalities found in these children were thought to be related to prematurity and multiple pregnancies -- not the procedure itself.

ICSI is used in cases in which the man's sperm is unable to penetrate the woman's egg. It involves the injection via a needle of a single sperm into the egg. Although approximately 20,000 babies have been conceived through ICSI since the early 1990s, concerns have been raised that the nature of the technique and the use of a single sperm that could be defective or immature could increase the risk of passing genetic defects from father to child.

In the study, published in this month's issue of Human Reproduction, author Ulla-Britt Wennerholm, MD, and colleagues studied more than 1,000 babies conceived with ICSI. They found that, compared with the general population, the risk of having any birth defect was 75% higher in the ICSI children.

The majority of the birth defects involved hypospadias, undescended testicles, and a heart condition known as patent ductus arteriosus (PDA). The last two conditions are directly related to preterm birth, and prematurity is known to be more common in twins. Therefore, the authors concluded that, aside from hypospadias, the "excess risk can to a large extent be explained by conditions associated with multiple and premature birth." More than a third of the babies in the study were multiple births.

Hypospadias, in which the opening through which urine passes is positioned on the underside of the penis or in the vagina, was the only birth defect thought to be possibly related to the ICSI procedure itself. The defect, which is most common in boys, is typically correctable with plastic surgery.

"We found a small increase in all malformations, but many of the malformations are minor, and we believe they are related to multiple births and preterm births," says Wennerholm, senior registrar at Sahlgrenska University Hospital in Goteborg, Sweden. She tells WebMD that the results of the study should be encouraging to infertile couples who have heard conflicting information about ICSI.


Along with the medical records of babies conceived through ICSI, Wennerholm and colleagues studied records of babies conceived without fertility treatments, and those conceived through conventional in vitro fertilization. The ICSI babies included 200 sets of twins, and one set of triplets.

Among the ISCI babies, a birth defect was identified in 87 (7.6%). Of these, only eight were considered severe.

Though the findings of only small rates of minor birth defects associated with ICSI are encouraging, concern remains about another aspect of the treatment. Some research has found a missing gene in men with very low sperm counts, suggesting that men with fertility problems who are helped through ICSI may pass on the fertility problem to their sons.

"It's a very important question that we were not able to look at with the kind of study we conducted," Wennerholm tells WebMD. "It will require prospective studies and chromosome analysis, and there are ethical questions to consider."

Wennerholm tells WebMD that her group is continuing to study the health of children born as a result of ICSI. Approximately 600 such children from around the world who have reached the age of 5 will undergo psychological and physical tests of their mental development, brain function, vision and hearing, as well as family relationships. A preliminary report of the study is expected in the next year.

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