Human Repeated Pregnancy Loss is Associated with Altered Olfaction

Introduction: In the Bruce effect, mice miscarry in response to bodily odors emitted from a male who did not father the pregnancy. About 1% of women experience recurrent pregnancy loss (RPL), which largely remains unexplained. In an ongoing study in our lab, RPL women displayed altered physiological and hormonal responses to body odors and synthetic social chemosignals, implying a possible link between RPL and olfaction.

Aim: In order to further investigate olfactory processing in women experiencing RPL, we conducted an olfaction MRI study in RPL women and matched controls.

Materials and methods: Twenty-two RPL women and 22 matched controls underwent MRI scans to measure olfactory bulb volume and sulcus depth (T2-weighted Turbo Spin-Echo sequence). Women completed a smell identification test (UPSIT) to assess their olfactory abilities of ordinary (non-social) odors; and will undergo synthetic social chemosignals discrimination tests.

Results: RPL women had 12.6% +/- 26% reduced volume of olfactory bulbs (t₄₂=2.92, p=0.0057) and 10.45% +/- 24% shorter olfactory sulci (t₄₂=2.85, p=0.007) than that of matched controls. Preliminary behavioral results suggest no difference between the groups in non-social olfactory abilities.

Conclusions: Our results suggest altered olfactory processing and neuroanatomy in women experiencing RPL. The results of this ongoing study may provide circumstantial support for a Bruce-like effect in humans.