Professor Robert Winston, head of the IVF unit at Hammersmith hospital, in west London, agreed to treat the woman, who is paying, after she was rejected by another hospital.
The patient, a former heroin addict in her 30s, is thought to have caught the virus from a boyfriend 10 years ago.
Professor Winston said the woman had been off drugs for eight years and had been in a "supportive" relationship for five years. He was initially reluctant to give her treatment because there was a chance she could develop full-blown Aids and die within a year of the birth. There is also a 10- 15 per cent chance of the virus being passed to the child.
A spokesman for the Terence Higgins Trust said that the couple would have gone through a long procedure before the treatment was approved.
But Dr Fleur Fisher, head of ethics, science and information for the British Medical Association, said the unborn child should be put first. "The issue is whether assisted reproductive technique should be used to help someone with a life threatening disease . . . Children need parents for a long time."Reuse content