Maybe it is a good thing we do not remember our births. Difficult ones can be traumatic and a major cause of brain damage. But researchers now suggest that a maternal hormone may protect our brains during birth, providing a natural safeguard against a problematic delivery.

A recent study of pregnant rats, led by Yehezkel Ben-Ari of the Mediterranean Institute of Neurobiology in Marseille, France, examined the effects of the hormone oxytocin. Oxytocin plays well-known roles in bonding between mates, thereby increasing trust among people--and a surge of the hormone can trigger the onset of labor. Ben-Ari's team found that during this same surge, oxytocin latches onto receptors in a fetus's brain. There the hormone acts somewhat like a tranquilizer and lowers the firing rate of a key class of neurons. "I have never seen such a strong inhibition," Ben-Ari says. The effect reaches its peak right before delivery, then wears off in a day.

This article was originally published with the title Another Reason to Thank Mom.

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