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Higher rate of major birth defects seen in ART infants: retrospective cohort study: attributed to parents' underlying infertility.

SAN ANTONIO -- Babies born as a result of assisted reproductive technologies had a significantly higher rate of major birth defects compared with children conceived naturally, according to a large, retrospective cohort study.

But the rate of birth defects was increased across various fertility treatments, including intrauterine insemination (IUI), suggesting that the increase may be a result of the parents' underlying infertility rather than a result of procedures used to treat it, study investigator Dr. Christine Olson said at the annual meeting of the American Society for Reproductive Medicine.

With the growing popularity of high-tech assisted reproduction techniques such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and zygote intrafallopian transfer (ZIFT), as well as the ovarian stimulation and gamete and embryo freezing protocols that go along with them, there has been much speculation that children born as a result of these procedures might be at higher risk for abnormalities.

Most studies of this population, however, have been reassuring, Dr. Olson of the University of Iowa, Iowa City, and her associates said in a poster presentation.

Her retrospective cohort study compared 1,466 children conceived through assisted reproductive technologies (ART), including IVF, ZIFT, and ICSI: 299 children conceived through IUI; and 8,289 children conceived naturally between 1989 and 2002.

"We tried to match controls to our cases so that we had a similar population, because that had been one criticism of the Hansen study," Dr. Olson said in an interview, referring to a smaller study published last year that found a doubling of birth defects among ART children (N. Engl. J. Med. 346[10]:725-30, 2002).

The control group in Dr. Olson's study was matched for maternal age, multiple or singleton pregnancy, year of the child's birth (plus or minus 2 years), and race.

The rate of major birth defects was 5.9% in the ART group, 5.0% in the IUI group, and 4.2% in controls.

"In our preliminary analysis, ART is associated with a small but significant increase in birth defects, and there is a similar increase for IUI but it isn't statistically significant probably because of the small numbers," she said. The consistency of birth defects across all infertility treatments--both high-tech and low-tech--is a strong argument that the defects may be directly linked to infertility rather than the procedure used to treat it, Dr. Olson added.

Of all the ART treatments, ICSI in particular has been scrutinized because the direct injection of a sperm into an egg bypasses several phases of normal fertilization, such as the acrosome reaction and sperm-egg binding and fusion. A separate poster presented at the meeting, however, showed no increase in either fetal abnormalities or obstetrical complications when comparing children conceived through ICSI versus IVF.

Among children conceived from 474 oocyte retrievals over 2 years at one ART program, there was no significant increase in abnormalities or fetal complications with ICSI, compared with IVF, reported Dr. Amin Khabani of the University of Washington, Seattle, and associates.

Still, the children were not specifically tested for chromosomal microdeletions, which is a risk in children whose fathers have severe male factor infertility, the researchers acknowledged.

A third poster evaluating the physical and mental development of 326 children conceived through IVF, ICSI, and frozen embryo transfer over an 8-year period (1995-2003) found they had slower physical development than children conceived naturally. Compared with naturally conceived babies, ART babies at birth had a significantly lower mean height (45.8 cm vs. 49 cm) and mean weight (2,440 g vs. 3,040 g), but by age 4-6 months, ART babies had caught up to the 50th percentile curve and continued at this growth rate until age 5 years, when follow-up ended.

Language and movement development was similar between ART and naturally-conceived infants, said Dr. Yukiko Nakajo of Ladies Clinic Kyono in Miyagi, Japan.
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Author:Johnson, Kate
Publication:OB GYN News
Date:Nov 15, 2003
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