Many medical scientists claim that the Pill protects against endometriosis and ovarian cancer. However, in her book Sexual Chemistry Dr Ellen Grant convincingly argues that the contraceptive pill may well be responsible for the development of endometriosis, in some cases."Although most contraceptive pills shrivel the womb lining, the blood vessels distort and dilate, which may encourage spread of endometrial tissue backwards through the veins," she said. "When the Pill is given up, the misplaced tissue thickens and bleeds more profusely causing more monthly pain which eventually leads to the diagnosis."

In the same way, she postulates, use of tampons, the long contraceptive cap (left in place longer than the conventional diaphragm) and having sexual intercourse during menstruation could also cause endometriosis.