Pregnancy Loss Tied to the Olfactory System?

• Position: SPONTANEOUS MISCARRIAGE

The odors we give off are a sort of body language--one that may affect our relationships more than we realize. Research from the lab of Noam Sobel at the Weizmann Institute of Science, Rehovot, Israel, suggests that this "chemical communication" may extend to human reproduction as well.

Sobel's study, published in eLife, found that women who suffer from a condition known as unexplained repeated pregnancy loss (uRPL) process messages concerning male body odor--especially their husband's--in a different way than other women. These findings may point to new directions in the search for causes and prevention of this poorly understood disorder.

Sobel and his team in the Department of Neurobiology thought that some cases of uRPL could be related to a human variation on the Bruce effect, named after its discoverer Hilda Bruce, who in 1959 found that when pregnant mice are exposed to the body odor of a male that did not father the pregnancy, they will almost always abort. Why this occurs is not fully understood, but the common rationale is that the female "chooses" to abort because the chemical message is that a new, "more fit" male is in town.

Could a similar effect occur in women? A remarkable estimated 50% of all human conceptions, and some 15% of documented human pregnancies, end in spontaneous miscarriage. Ethical considerations obviously prevented the researchers from repeating the Bruce experiments in humans; the team instead sought circumstantial evidence.

For the Bruce effect to occur in mice, the female must remember the body odor of the fathering male. To test for this in humans, the researchers presented participants with three odorants: one extracted from a t-shirt worn by their spouse and two from t-shirts worn by other men. They found that women with uRPL were able to identify their spouse by smell, while the control women could not.

The ability of uRPL women to identify their spouse by smell was remarkable. In a part of the experiment where the women did not know what odors they would be smelling, "several of these women...