- A woman's body could reject the sperm of less suitable male partners.
- Sperm is more likely to fail if the woman had not been exposed to that man's semen for at least three months.
- The research could lead to improved treatments for infertility and miscarriages.
A woman's body may be unconsciously selective about sperm, allowing some men's to progress to pregnancy but killing off the chances of less suitable matches, an Australian researcher said Wednesday.
University of Adelaide professor Sarah Robertson said her research suggested that sperm contains "signaling molecules" that activate immunity changes in a woman so her body accepts it.
But some apparently healthy sperm failed to activate these changes, leading to the suggestion that the female system can be "choosy" about its biological mate, she said.
"It's rather like a two-way dance," Robertson said.
"The male provides information that increases the chances of conception and progression to pregnancy, but the female body has a quality control system which needs convincing that his sperm is compatible," she added. "That's where the dance can go wrong with some couples -- if the male signals are not strong enough, or if the female system is too 'choosy'."