Born Face Up or Face Down; More or Less Pain

The gemora (Niddah 31a) asserts two differences in birth between between boys and girls. Firstly, boys emerge from the natal canal face-down, whereas girls emerge face-up.
("זו הופכת פניה וזה אין הופך פניו")

Secondly, regarding the pain of labor, delivery of a boy is easier to suffer through than is a girl's.
("חבלי נקבה מרובין משל זכר")

How do these two facts dovetail? What does face up or down have to do with pangs of labor during childbirth?

The behavior of each differs just before they leave the womb. The newborn girl, just before the final thrusts force her out of the dilated cervix, turns her face sideways, always angling her body to emerge face-up. That extra struggle to turn 180 degrees along the descending axis, during the descent of the head into the cervical opening and along the vaginal canal, is what apparently adds to the pain, besides the usual contractions and tissue tears.

The boy's delivery, on the other hand, is more like a downwards dive without any body-twisting along the way out, keeping the head's orientation as usual, face down, so the head comes out first and face-down.


I don't know of empirical evidence that confirms this phenomenon, as our sages assert.

Of course, in real life, variations exist. For example, the head can emerge facing sideways - in which case it's neither face-up nor face-down.