Women on the pill may pick the wrong partner

In research involving almost a hundred women, scientists in the UK say the contraceptive pill could lead to women choosing the wrong partners.

While other research has shown that women appear to prefer the body odour of men who are genetically dissimilar to themselves, contraceptive pill-users preferred relatively similar men.

The suggestion is that women may instinctively use smell to identify people with different immune systems and complementary genes - therefore if pill users have an altered preference and choice of partner, the resulting genetic similarity between partners could cause fertility issues.

The study by Liverpool and Newcastle university researchers suggests the pill disrupts the selection process and as odour perception plays a significant role in maintaining attraction to partners, it could ultimately lead to the breakdown of relationships when women stop using the contraceptive pill.

Lead researcher Dr. Craig Roberts says by passing on a wide-ranging set of immune system genes, couples increase their chances of having a healthy child that is not vulnerable to infection and partners with different genes are also less likely to experience fertility problems or miscarriages.

The researchers say major histocompatability complex cluster of genes which helps build proteins involved in the body's immune response is also known to influence smell signals called pheromones and this leads women to use their sense of smell in helping to choose partners.

In a test carried out before and after the women had started taking the pill, they asked the women to sniff six male body odour samples and say which one they preferred and the two sets of results were very different.

The researchers suspect that the results were related to the way the pill simulates a state of pregnancy in women and once pregnant, the need for a compatible partner for children recedes.

The research is published in the Proceedings of the Royal Society B journal.