Infants conceived with techniques commonly used in fertility clinics are two to four times more likely to have certain birth defects than are infants conceived naturally, a new study has found.

The defects included heart problems, cleft lip, cleft palate and abnormalities in the esophagus or rectum. But those conditions are rare to begin with, generally occurring no more than once in 700 births, so the overall risk was still low, even after the fertility treatments.

The procedures that increased the risk were so-called assisted reproductive techniques, like in vitro fertilization, which require doctors and technicians to work with eggs and sperm outside the body. The study did not include women who only took fertility drugs and did not have procedures performed.

Women considering fertility treatment should be informed that there might be a risk of birth defects, Dr. Alan R. Fleischman, vice president and medical director of the March of Dimes said, but they need not be “overly concerned.”