Pregnancy odour to reveal unborn baby's sex

The study suggests that some female primates release a natural "pregnancy perfume" that males can probably detect and such scents appear to broadcast whether the mom-to-be is carrying a boy or a girl, the Discovery reported.

Authors Jeremy Crawford from the University of California and Christine Drea from Duke University wrote that the scent signatures may help guide social interactions, potentially promoting mother-infant recognition, reducing intragroup conflict or sort out paternity.

The latter presents a loaded scenario, as it could be that males can sense, even before the birth, whether they fathered the baby. The researchers additionally suspect that odours advertising fetal sex may help dads and moms prepare for what's to come.

They found that expectant lemur moms give off simpler scents that contain fewer odor compounds compared with their pre-pregnancy bouquet. The change is more pronounced when the moms are carrying boys, Drea said.

She and Crawford found that the patterns correlate with changes in blood hormone levels. The difference in hormone profiles between pregnant lemurs carrying sons and those carrying daughters is dramatic.

Lemurs are not regarded as being the best scent-detectors, so it could also be that the release of the odours and detection of them are quite common throughout the animal kingdom.

The study is published in the journal Biology Letters.