A way of preserving the chances of having a child for women and girls facing cancer treatment that will leave them infertile has been demonstrated to work, for the first time.

Specialists at McGill University in Montreal have developed a protocol in which they retrieve immature eggs (i.e., "oocytes") from a woman's ovaries, induce the oocytes to mature in a lab dish, then deep-freeze them; the oocytes can then be thawed for fertilization at a future point.

This strategy avoids the rise in estrogen that is necessary for normal ovulation but which can be detrimental for cancer patients, and doesn't require cancer treatment to be delayed.

Furthermore, because eggs and not embryos are being preserved, there's no need for donor sperm or a male partner at that point, which is an attractive option for young cancer patients, Dr. Seang Lin Tan and associates explain in the medical journal Fertility and Sterility.

They report the case of a 27-year-old woman who had a history of problems becoming pregnant. Although she did not have cancer, she agreed to try the new approach.

Her doctors retrieved 18 immature oocytes from the woman after hormone treatment, and these were cultured for 48 hours in a maturation medium. Seventeen of the oocytes were then cryopreserved in liquid nitrogen.

Subsequently, four eggs survived when they were thawed 2 months later. Three were fertilized by injection of a single sperm, and transferred to the patient's womb 2 days later.

At 39 weeks gestation, the patient delivered a healthy 7.5-pound baby girl. "Examination of the newborn by a pediatrician found no evidence of congenital malformations, and the child has continued to develop normally," Dr. Tan's team reports.