A brain-dead American woman was disconnected from life support and died a day after giving birth to a girl in a hospital in Virginia.

Susan Torres, 26, gave birth on Tuesday by caesarean section. She was being kept alive to allow her fetus to develop, after suffering a stroke on May 7 while four months pregnant with her second child.

"This is obviously a bittersweet time for our family," Justin Torres, her brother-in-law, said in a statement Wednesday.

The baby was born without complications two months premature. Susan Anne Catherine Torres weighed 800 grams, or 1 lb., 13 oz.

"The baby is doing well," said a message on the family website.

The mother's stroke was caused by an undiagnosed melanoma cancer, which had spread to her brain.

Her husband, Jason Torres, agreed to an offer from doctors to keep his wife alive for the sake of the baby. He left his job to be at the side of his wife, who had been a researcher at the National Institutes of Health before her illness worsened.

Mother and baby were at the Virginia Hospital Center in Arlington, about 160 kilometres north of Richmond.

The hospital declined to release information about the mother's condition or whether she was still hooked up to life support. The entire staff was "delighted with the successful delivery," the hospital said in a statement.

English medical journals have documented at least a dozen cases since 1979 of a woman being kept alive on life support equipment to deliver a baby, according to Dr. Winston Campbell, director of maternal-fetal medicine at the University of Connecticut Health Center.

Facing huge medical bills not covered by insurance, the Torres family has benefited from about $400,000 US in donations collected from around the world through a website.