Fertility clinics and egg-donor agencies advertise broadly, especially on college campuses and even on New York subways, for donors, who are typically paid $5,000 to $10,000 for each donation, even more if the woman satisfies a fertility client’s specifications. One woman wrote in The Atlantic that she had responded to an offer for $25,000 in The Yale Daily News for “a young woman over five feet five, of Jewish heritage, athletic, with a combined SAT score of 1500, and attractive.”

Donor eggs are typically used for women seeking pregnancy who may have undergone early menopause, have poor egg quality, a history of genetic disease, a hormonal imbalance, ovaries that fail to respond to stimulation, or are over the age of 40.

“Egg donors are just not on anyone’s radar,” Dr. Schneider, who lives in Tucson and is certified in internal medicine, addiction medicine and pain management, said in an interview. “It’s not the same as sperm donation, which doesn’t involve hormone injections or any invasive treatments. In my opinion, egg donors need to be treated like all other organ donors — their health should be monitored.”

What we have now are only anecdotal reports of women who served as egg donors and later developed cancer. For example, five years before Ms. Wing’s untimely death, two doctors at a London fertility clinic described in the journal Human Reproduction the “tragic case of a young woman who died of cancer of the colon after successfully donating eggs to her younger sister.” They noted that long-term safety concerns about egg donation had been raised in the British Medical Journal (now BMJ) in 1989, given the high levels of hormones administered to donors.

The London doctors, K.K. Ahuja and E.G. Simons of Cromwell Hospital, called upon the British Human Fertilization and Embryology Authority “to confirm that ovarian stimulation in volunteer egg donors does not increase the risk of cancer over and above the background rate.” But this has yet to be done.

Earlier this year, in Reproductive Biomedicine Online, Dr. Schneider and two co-authors reported on five cases of breast cancer among egg donors, four of them women in their 30s and all five of whom had no apparent genetic risk for the disease. None of the women had been given any information about long-term risks of egg donation, because no such information exists.

The authors pointed out that single cases do not establish whether hormone stimulation of egg donors increases the risk of various cancers, and reiterated Dr. Schneider’s earlier pleas for “the need to create egg donor registries that will facilitate long-term studies on egg donors.”