Raises Birth-Defect Risk
MARILYNN MARCHIONE / AP / Seattle Times 9feb2007
SAN FRANCISCO — Babies conceived through fertility treatments have higher rates of birth defects, but the overall risk is so small that it should not keep couples from having children this way, doctors say.
The news comes from a study of more than 61,000 births in Canada, the largest ever done on this in North America.
"What's important and reassuring is that the absolute risks are still low," at less than 3 percent of all births, said one of the study's leaders, Dr. Mark Walker of the University of Ottawa.
Even so, the risks of certain defects were startlingly high for babies born with the help of technology.
Couples who want to lower the risk should have only one or two embryos implanted at a time, specialists said. The danger of defects from multiple births is far greater than any risk posed by the fertility treatments themselves.
Results of the study were to be reported today at a meeting of the Society for Maternal-Fetal Medicine in San Francisco.
More than 1 million babies worldwide [see sidebar] have been born through assisted reproductive technology, or ART. This includes induced ovulation, artificial insemination, IVF or in vitro fertilization, and more advanced methods such as injecting a single sperm into an egg to create an embryo.
Such techniques are used in as many as 1 percent to 2 percent of births in the United States and Canada. They already are known to raise the risk of premature birth and other complications.
But studies have been divided over whether they increase the likelihood of birth defects.
The Canadian work is important because it's a large study and quantifies the risk of specific birth defects, "a first as far as I know," said Dr. Nancy Green, medical director of the March of Dimes.
Researchers studied 61,208 births in Ontario during 2005, including 1,394 that resulted from fertility treatments. They looked at rates of birth defects and adjusted estimates of risk to reflect differences in the mothers' ages, whether they smoked, the gender of the babies, birth complications and other factors.
Nearly 3 percent of ART babies had a birth defect versus just under 2 percent for babies conceived naturally. That translated to a 58 percent greater risk. The chances of a defect rose as the complexity of reproductive help did — they were highest for IVF and lowest for simply giving medications to spur a woman's ovaries to make more eggs.
The biggest difference was seen in the rate of gastrointestinal problems, such as defects in the abdominal wall or organs not in the right place. Babies conceived through ART were nearly nine times more likely to have such problems — one in 200 births versus six per 10,000 for the others.
However, "it's still pretty uncommon," said lead researcher Darine El-Chaar of the University of Ottawa.
The chance of cardiovascular defects was more than twice as high — 90 per 10,000 babies conceived through ART versus 40 among those conceived naturally. Defects such as malformed limbs also were slightly more common, but not facial defects such as cleft palate or problems such as spina bifida.
The researchers note that people who have trouble conceiving also may have underlying genetic or health factors that could partly account for the higher rates of birth defects.
Multiple Births Pose Health Risk to Moms
CTV Television (Ontario, Canada) 1dec2004
CTV.ca News Staff — There could be deadly complications for women who become pregnant with twins, triplets or greater multiple births, a new study warns.
Multiples research usually focuses on the babies. It has long been known that twins, triplets and babies from other multiple births are more likely to suffer health problems than "singletons."
The new study was done by the Ottawa Hospital and the University of Ottawa. It is the first major review of the mothers' health.
Some of the findings regarding women carrying multiples:
- They are four times more likely to have a heart attack during pregnancy
- 13 times more likely to suffer heart failure
- 2½ times more likely to develop deep vein thrombosis, blood clots in the legs or lungs
- Have a greater risk of developing water in their lungs, high blood pressure, and post delivery bleeding
Dr. Mark Walker, a researcher with the Ottawa Health Research Institute, wrote the study with colleagues from Health Canada, and the Universities of Toronto and Ottawa.
In an interview with CJOH, Walker said mothers expecting more than one child should watch for warning signs -- pain in their legs, shortness of breath or chest pains.
"With a single baby during pregnancy, the heart's output increases by about 40 per cent," Walker said. "The blood becomes more coagulable (thicker), all preparing for delivery … when you have two or three babies, that increases that much more. That much more stress on the body."
About half of all twins and most sets of triplets are the result of fertility drugs or treatments that implant more than one embryo to improve the odds of having a viable pregnancy.
Dr. Jon Barrett of Sunnybrook and Women's College Hospital said women considering IVF or other techniques should be reminded of the risks.
The study was published Wednesday in the British Journal of Obstetrics and Gynecology.
With files from CTV's Avis Favaro and CJOH's Norman Fetterley