CHICAGO — Babies born to couples who rely on medical technology to become pregnant have much higher rates of certain birth defects, according to a study published online Monday in the journal Human Reproduction.
The report from the federal Centers for Disease Control and Prevention found these infants have twice as many heart defects and cleft lips and nearly four times as many gastrointestinal defects as those conceived without technological interventions.
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Still, the overall rate of the defects was low and the majority of babies born to couples using assisted reproduction were normal, said Jennita Reehfuis, a CDC epidemiologist and lead author of the report.
Independent experts noted the study establishes an association, not a causal connection, between birth defects and two procedures: in vitro fertilization and intra-cytoplasmic sperm injection. (With IVF, a man's sperm and a woman's egg are merged outside the body. ICSI involves injecting a single sperm into an egg. In both cases, resulting embryos are then implanted in a woman.)
It's possible that couples who turn to these interventions have chromosomal abnormalities that explain their infertility as well as the risks to offspring, said Dr. Elizabeth Ginsburg, president of the Society for Assisted Reproductive Technology and medical director of the IVF program at Brigham and Women's Hospital in Boston.
"This study doesn't get to the question of whether these outcomes are due to the procedures themselves or the population of people who struggle with infertility," she said.
Because it's well established that carrying twins or triplets increases the risk of birth defects, the CDC study looked only at pregnancies that resulted in a single birth. More than 14,000 women from 10 states were included in the analysis, of which 281 used assisted reproduction.
Data were adjusted for other factors that might affect birth defect rates, including a woman's age, race, body mass index and history of miscarriages.
The findings add to a growing body of evidence suggesting that birth defects are linked with the increasingly common medical technologies that help infertile couples. In 2005, the latest year for which data are available, 52,000 babies were born in the United States through assisted reproduction.
A study from Western Australia published in the New England Journal of Medicine in 2002 showed that 8.6 percent of babies conceived through ICSI and 9 percent of those conceived through IVF had a major birth defect by the age of 1, compared with 4.2 percent of infants conceived the old-fashioned way.
In 2005, a study in Fertility and Sterility by researchers at the University of Iowa found that IVF babies have a 6.2 percent risk of having a birth defect, compared with a 4.4 percent risk for naturally conceived infants.
That same year, a broad analysis of several studies concluded that babies conceived through assisted reproduction had a 40 percent higher risk of birth defects. However, another study in Obstetrics & Gynecology determined that women using assisted reproductive technologies were at no higher risk of giving birth to infants with "chromosomal or structural abnormalities."
For infertile couples considering medical help, the bottom line is "there may be a risk of adverse outcomes to offspring" and this should factor into their decision-making, Ginsburg said.