Sperm can 'convince' a woman to accept pregnancy.

Sperm are commonly thought to have only one function in reproduction: to fertilize the female's egg, but new research from the University of Adelaide contradicts this notion.

New research published in the Nature Research journal Communications Biology shows that sperm can send signals directly to female reproductive tissues, increasing the likelihood of conception.

"This research is the first to show that signals in sperm persuade the female immune response to allow the male partner to fertilize her eggs and produce a pregnancy," said project leader Professor Sarah Robertson of the Robinson Research Institute.

"This contradicts our existing concept of sperm's capabilities: they are not just carriers of genetic material, but also agents for persuading a female to invest reproductive resources in that male."

Proteins in seminal fluid have long been thought to influence the female immunological response during conception, allowing her body to accept the foreign embryo. Until now, it was unclear if sperm influences this response.

After mating with men with intact sperm or vasectomized males, the researchers looked at the impact on global gene expression in the mouse uterus. Intact males triggered more alterations in female genes, altering immune response pathways in particular.

Females who came into contact with sperm showed higher immunological tolerance than females who mated with vasectomized males. The researchers confirmed that sperm were directly responsible by looking at the consequences of sperm interactions with female cells in cell culture tests.

These new findings imply that sperm health is vital not only for conceiving, but also for having a healthy baby down the road. Age, nutrition, weight, alcohol and smoking, as well as exposure to environmental pollutants, can all alter sperm quality in males, which may have more implications for pregnancy health than previously thought.

Professor Robertson explained, "Recognition that sperm impact reproductive events beyond merely fertilizing oocytes reveals that sperm quality can have ramifications for pregnancy health, beyond just conception."

"Conditions such as recurrent miscarriage, hypertension, preterm birth, and stillbirth are influenced by the female's immunological response in ways that the partner's sperm have a role in."