The science of sex
Sex is a form of biological communication, and women use it to make decisions on whether to invest in a pregnancy, explains Sarah Robertson, Professor and Director, Robinson Research Institute, University of Adelaide.
The act of penetrative sex has evolved over millions of years as a mechanism to deliver sperm to eggs and initiate pregnancy. But there’s more to sex than just the meeting of two sets of genes. Here’s how a woman’s immune system responds to sexual intercourse and facilitates healthy pregnancy.
Most people think just one sperm is needed to fertilise a woman’s egg and make a healthy pregnancy. This underpins a common view that all the other sperm – and all the other sex – are surplus to requirements, at least when it comes to conceiving a pregnancy.
However, biologists now believe sexual intercourse is not just a sperm delivery process, but also a kind of biological communication. Regardless of whether fertilisation occurs, sperm and other components of the ejaculated fluid trigger subtle changes in the immune system of women.
This has consequences for pregnancy should it happen later. More broadly, the importance of regular sexual activity also has implications for fertility planning, and for IVF and other forms of assisted reproduction, which generally do not take sexual practise or history into account.