British fertility experts were growing increasingly concerned about the risks posed by "intensive farming" of human eggs from women after one donor produced 85 in a single session.

As well as causing mood swings, headaches and tiredness, the drugs used to create superovulation can, in a small number of cases, lead to a potentially fatal condition called ovarian hyperstimulation syndrome (OHSS). The risk increases as more eggs are produced.

Despite that, donors in the UK, some of whom receive payment or a free cycle of IVF, are producing record numbers of eggs in a single cycle, raising fears that clinics are exploiting them to achieve the maximum return on their investment. Payments for donors in Britain are being tripled to $1,195 for a course of donations.

The latest available figures from the Human Fertilization and Embryology Authority, the British government's fertility watchdog, show that as well as the case of the woman from whom 85 eggs were harvested, another produced 80 eggs in a single session. Three more women had between 70 and 72 eggs removed.

Studies show that once a woman who has been given the powerful drugs to increase ovulation produces more than 20 egg sacs, which house the eggs needed to create an IVF embryo, she has an 85 percent chance of developing OHSS.

The condition, in which fluid accumulates in the abdomen, can lead to blood clots and kidney damage and, in some rare cases, death.

One 35-year-old woman, who suffered OHSS after an IVF treatment cycle on Britain's National Health Service forced her to produce 50 eggs, said, "I felt like the doctor treated me as if I was a machine. He was looking at me as if I was an animal on that operating table, just producing eggs."

The woman, a married teacher from London, said the risks of the process were never fully explained to her. Three months after IVF, her stomach was so swollen that she appeared pregnant even though she was not.

Richard Kennedy, chairman of the practice committee of the International Federation of Fertility Societies, said, "This complication [OHSS] is unique to IVF and is potentially fatal. It is particularly relevant to egg donors because they are younger and more fertile, therefore they are more at risk of OHSS."

He added, "There could reasonably be a temptation to try to be more aggressive in stimulation regimes in these women to make sure you get a lot of eggs."