Smells are a type of body language that can affect our relationships more than we thought. A new study by Israeli scientists found that the brains of women with unexplained repetitive pregnancy loss process male body-odor in a different way.
It is currently estimated that 50% of all conceptions and 15% of documented pregnancies end in spontaneous termination. Israeli Professor Noam Sobel and his team at the Weizmann Institute of Science suggest that some of these cases could be linked to a human variety of the Bruce effect, which usually occurs in mice.
This effect was discovered by scientist Hilda Bruce in 1959 and was later named after her. In that year, the British woman realized that pregnant mice almost always lost their pregnancies after being exposed to men’s body odor who was not the father of their babies.
In their research, Israeli scientists tried to see if this phenomenon can also occur in humans. Obviously, for ethical reasons, Bruce’s human experiments could not be repeated. However, Sobel’s team sought other circumstantial evidence.
In particular, they had two groups of women sniff out three odors: one extracted from a T-shirt worn by their spouse and two from unknown men, according to the study published in the journal eLife.
Additional evidence suggests that women who had repeatedly lost their babies were not only better at identifying their spouse’s odor, but could also perceive men’s body odor in a totally different way. When asked to rate male body odors on various scales, based on pleasure and intensity, or by estimating factors such as fertility or sexual attractiveness, women in the first group were better able to describe and classify them.
In the final phase of the research, Israeli scientists analyzed structural and functional images of the brain. Analysis of the former revealed that women who had lost their children had smaller olfactory bulbs. It is a type of relay that the brain uses to sniff.
By studying the functional images, the researchers detected a greater response to masculine odors in the hypothalamus of women who experienced spontaneous pregnancy termination. And it is precisely the hypothalamus that plays a key role in producing the Bruce effect in mice. This same region of the brain participates, among other things, in the coordination of pregnancy and hormonal regulation.
“It seems these losses of pregnancy may be ‘unexplained’ because physicians are looking for problems in the uterus, when they should also be looking in the brain, and particularly the olfactory brain” says Weissgross. Sobel cautions: “Correlation is not causation, so our findings do not prove in any way that the olfactory system, or body-odors, cause miscarriage. But our findings do point to a novel and potentially important direction for research in this poorly managed condition,” said study co-author Reut Weissgross.