Scientists discover why regular sex prior to conception reduces pregnancy complications

A man may contribute more than just sperm to the process of conception, research suggests.

Presenting the work at a conference, Professor Sarah Robertson from the University of Adelaide in Australia confirmed that repeated exposure to a partner's seminal fluid before conception leads to a lower chance of complications, including miscarriage and pre-eclampsia, during early pregnancy.

'We now know that an average of at least three to six months coitus with their partner is necessary to get their immune system to respond correctly to enable a healthy pregnancy', said Professor Robertson.

Professor Robertson further compared the implications of pregnancy on the immune system of the mother with those arising from an organ transplant, saying pregnancy involved 'foreign tissue living in a female body for nine months and so you have to have transplantation tolerance or immune tolerance to allow that to occur'.

Sex prior to conception is thought to expose the female immune system to the immunological signature of her partner and thus help establish that immune tolerance.

But just how the exposure to the partner's seminal fluid does this is unclear. Research done in Professor Robertson's lab suggests that small RNA molecules, called micro RNA, in semen may interact with cells in the female reproductive tract. At this point, Professor Robertson says, the micro RNA can alter gene expression and modify tissue function to bring about the immune changes.

The work may have implications for research into currently unexplained problems in early pregnancy. The abstract for Professor Robertson's talk at the conference suggests that 'pathologies of pregnancy such as implantation failure or recurrent miscarriage may be due to inadequate male-female seminal fluid communication, or over-zealous female quality control'.

Professor Robertson stressed that, when it came to pre-conception sex, 'it's not so much about the likelihood of getting pregnant, it's more about health progression of pregnancy'.