Babies conceived using in vitro fertilization are two to four
times as likely to have certain birth defects than those conceived
naturally, US researchers said.
In vitro babies are two to three times as likely to be born with cardiac defects involving a hole in the heart, according to researchers led by epidemiologist Jennita Reefhuis of the US Centers for Disease Control and Prevention.
These babies also are also twice as likely to be born with a cleft lip and four times as likely to be born with some gastrointestinal defects, the researchers wrote in the journal Human Reproduction.
Even with the increased risk, however, the defects remain rare in these babies and the cause of the increased risk remained unclear, the researchers said.
In vitro fertilization involves placing egg and sperm cells in a laboratory dish, then transferring the resulting embryo into a woman's uterus.
"Any couple who is considering these treatments wants to be aware of all the pros and cons of the treatment," Reefhuis said in a telephone interview.
"And, so far, the main cons that have been known have been the increased risk of having twins and other higher multiples, which has its own share of problems. I think it's important for couples to be aware that there may be some increased risk for birth defects as well."
Many infertile couples turn to in vitro fertilization and about 50,000 such infants are born each year in the United States - a number that has roughly doubled over the past decade.
About one percent of US babies are conceived using the
technique, the researchers said.
The study involved 281 babies conceived using in vitro fertilization, or a less-common technique called intracytoplasmic sperm injection, and 14,095 babies conceived without infertility treatments.
The babies were single births, not twins, triplets or other multiple births.
Babies born as part of any multiple birth already are at higher risk for birth defects.
The researchers determined that using in vitro fertilization did
not significantly increase the chances of birth defects among the
The study did not look at babies born to women who took ovulation-stimulating drugs or used artificial insemination.