A new study claims to have found women who give oral sex to their partners more often are more likely not to suffer recurrent miscarriages.
While this might sound like a fabricated tale, researchers believe swallowing semen strengthens a pregnant woman's immune system.
According to a report in the Journal of Reproductive Immunology, scientists at Leiden University Medical Centre, Netherlands noted this in turn makes fetuses more likely to grow healthily.
They argued semen contains hormones and proteins from the man's body which are useful for the mother to build up a tolerance to antigens such as human leukocyte antigens (HLA).
“This study suggests a possible protective role of oral sex in the occurrence of recurrent miscarriage in a proportion of the cases,” the study authors said.
"Our results suggest an association between less oral sex and the occurrence of recurrent miscarriage," they added.
By building up the mother's tolerance to substances from the man's body, the parents could give a foetus – half-made of the father's DNA – a better chance of thriving.
This could, the theory explains, make the mother's immune system less likely to reject the baby and lead to its death.
The report further indicated although semen may be better absorbed in the gut, vaginal exposure to semen could also play an important role in a couple trying to conceive.
The researchers tested their theory comparing the pregnancy history and oral sex habits of 234 women.
They, however, acknowledged the study was small and did not provide evidence that swallowing sperm was leading to the lower miscarriage rate.
But they believe their results are strong enough to suggest a link between the two and warrant more research.
Of the 234, some 97 of the women had suffered from recurrent miscarriage and were also giving their men low oral sex.
While 73% of women in the non-miscarriage group regularly gave oral sex, only 57% of those in the miscarriage group did.