Women avoid their fathers when they are most likely to get pregnant, a new study found.

Is this nature’s way to prevent inbreeding? Or is it just that girls steer clear of their overbearing dads when they'd rather be with their boyfriends?

"Women call their dads less frequently on high-fertility days and hang up sooner if their dads call," says Martie Haselton, co-author of the paper in the journal Psychological Science.

Avoiding inbreeding... 
Debra Lieberman, the paper's main author, thinks that the women in the study are instinctively avoiding their dads around the time they're ovulating to avoid inbreeding - it's nature’s way of preventing sick babies being born.

The children of closely related couples have more chance of birth defects than children of unrelated parents. This is why marrying or having sexual relationships with close relatives is often considered harmful.

In many cultures around the world, marrying a relative is common. In India, Tanzania, and Nigeria, second cousins often marry. But this may be because in these countries, women tend to have more children, so they may worry less about birth defects.

...or bossy dads?
Women might also want to avoid Dad to stop him keeping too close a watch on their boyfriends. In many cultures a woman’s father may see his role as guarding his daughter’s sexuality. She might keep out of his way so he doesn't scare off prospective mates.

Whatever the reason that women steer clear of their fathers when they're most fertile, the result is more babies. The findings show it boosts their chances of meeting sexual partners and getting pregnant.
 

Do you notice your menstrual cycle affects the way you behave? Leave a comment here or join the discussion on Facebook.