Women who meet their partners while taking birth control pills are more dissatisfied with their sex lives and more likely to end the relationship, according to new research. It included 2,519 women, mainly from the USA and the Czech Republic. The results found that those who started dating the father of their first child while taking contraceptive pills experienced sexual dissatisfaction with the relationship. In addition, they are also less attracted to their intimate partner, compared to women who do not take birth control pills. In previous research, scientists have found that a woman’s menstrual cycle influences the type of man she is most attracted to. Part of the chemistry between two people is also in liking the partner’s smell, which is determined by the MHC molecule, part of the immune system. Scientists explain that we are attracted to the opposite sex with a scent different from ours, because in this way the chances of survival of the generation that is being created are greater. This helps the “diversity” of genes and the resilience of the offspring’s immune system. Taking contraceptive pills, however, puts the body in a state similar to pregnancy. Pregnant women, in turn, tend to prefer MHC scents similar to their own. The likely explanation is that in this way they feel comfortable and safe, surrounded by supportive relatives. NEWS_MORE_BOX This means that a man may find himself attractive to a woman on the pill, only to find that he is “not her type” when she gets her period. Of course, there are many variables involved in choosing a partner, and the influence of birth control pills is hardly decisive. They could have the biggest impact on attitudes towards sex. Scientists advise ladies to stop taking the pill a few months before marriage to make sure they are still sexually attracted to their partner. The research is published in the Proceedings of the Royal Society B.