Kissing spreads bugs that protect pregnancy

Kissing was created to spread germs which build up immunity to illness, believe scientists. The loved-up gesture allows a bug, which is dangerous in pregnancy, to be passed from man to woman to give her time to build up protection against it. The bug, Cytomegalovirus, is found in saliva and generally causes no problems. However, it can turn nasty if caught while pregnant and can kill unborn babies or cause birth defects.

Researcher Dr Colin Hendrie from the University of Leeds, said: "Female inoculation with a specific male's cytomegalovirus is most efficiently achieved through mouth-to-mouth contact and saliva exchange, particularly where the flow of saliva is from the male to the typically shorter female."