According to AFP:
PARIS (AFP) — Contraceptive pills taken by tens of millions of women around the world can disrupt the innate ability to sniff out a genetically compatible partner, a study released Wednesday has found.
Normally women are instinctively attracted, via their sense of smell, to men who have a dissimilar genetic makeup.
Overly similar gene profiles can result in difficulty trying to conceive a child, an increased risk of miscarriage and a weaker immune system, earlier research has shown.
A group of about 140 genes in an area called the Major Histocompatibility Complex (MHC) — which helps build proteins involved in the body’s immune response — also plays a key role in odour through interaction with skin bacteria.
How these genes are expressed can help determine which individuals, unknowingly following their nose, find us attractive.
A team led by Craig Roberts at the University of Newcastle, England, conducted an experiment to find out if taking the pill influences odour preferences.