A Bradford hospital doctor today reinforced warnings that sex can kill women who have just given birth.

Extensive research partly undertaken by Dr Philip Batman has highlighted that lovemaking before the woman's womb has returned to its normal state can cause potentially fatal air "bubbles" in major heart and brain arteries and blood clots in the womb.

The results of his findings, published today in the British Medical Journal's Postgraduate Medical Journal, detail the cases of two young women who died suddenly while having sex within days of giving birth.

A 22-year-old woman died eight days after having her third child and a 29-year-old died five days after the birth of her fourth child. Both women had suffered air embolisms and blood clots.

Couples are normally advised that it is safe to resume intercourse five or six weeks after the birth of their baby.

The report by Dr Batman, a consultant pathologist at Bradford Royal Infirmary, says although there are moves to issue more general guidelines about the resumption of sex it would be wise to warn mothers about the dangers of doing so too soon.

"We want to reassure mothers that these deaths took place a number of years ago and that incidents like these are thankfully extremely rare," he said.

"However, because of the tragic circumstances surrounding both cases we felt it was in the public interest to draw the attention of mothers to the potential dangers of intercourse in the early days after childbirth."

Dr Batman said death during sexual intercourse was rare and was mainly associated with middle-aged men with heart disease.

The research also found that sex in the knee-chest position - in which the woman kneels, with her face down - should particularly be avoided in the first weeks after childbirth as the position raised the womb above the right side of the heart.

Alan Hobbs, assistant chief executive of Dewsbury District Hospital where one of the dead women cited in the report was taken, said the report would publicise the incidents to other doctors.

He said advice about sexual intercourse was given to women who had given birth at the hospital and he hoped other hospitals would pass on the dangers to their patients in light of the two deaths.

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