Headlines this week draw attention to a new reason for second thoughts about the contraceptive pill -- one that may carry weight with people who reject loftier arguments. This one comes from biologists.

It seems that the pill may change the way a woman reacts to a man’s smell. A man’s aroma can give a clue to his type of genes and ability to fight disease, although it is complicated by factors such as soap and aftershave. In a world without such refinements and the pill, women subconsciously react to a man’s smell to identify a partner with dissimilar genes to their own. It is important to have a mixed immune system (called the Major Histocompatibility Complex or MHC) to combat different diseases, but taking the pill could disrupt this natural ability, according to research from the University of Liverpool in England. Possible results are difficulty in conceiving, an increased risk of miscarriage and long intervals between pregnancies. Passing on a lack of diverse genes to a child could also weaken their immune system.

The research did not find that women who were not on the pill were more attracted to men with a different MHC, but it did show clearly that the pill made women more likely to be attracted to a man with a similar immune makeup. Lead researcher Dr Craig Roberts said MHC similarity could not only lead to fertility problems but could ultimately lead to the breakdown of relationships when women stopped taking the pill and discovered they did not like the smell of their partner. “Divorce rates were certainly lower before and up to the mid-60s when pill use became commonplace, but as you can imagine, there are plenty of alternative explanations for increasing divorce rates since then.”

Comment: Yes, but the pill is still the prime suspect -- not so much for its biological effects as for its effect on values relating to marriage and children. Dr Roberts is seeking funding for a “definitive study” on the pill and MHC, but it is doubtful that the results will provide a solution to divorce rates. ~ Telegraph (UK), August 13