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 are reporting.

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 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 twin, triplet and other 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.