The reasons for not hatting (adapted from Carla Harlty):
1.Hats can be very dangerous. They can cause moms to have postpartum hemorrhaging. As it turns out the experience of birth is what triggers the built in safety mechanisms. This is also true for third stage. Mom being able to smell her newborn’s head is the design for the reconnection of mother and baby (smell of baby to olfactory system to limbic system = initiation of “identification” biology) and release of Oxytocin signaling the uterus to release placenta and stop bleeding so necessary for mother’s health. The smell doesn't so much trigger Oxytocin as it is that the limbic system is waiting for that smell in order to tell the uterus it is ok to proceed to the next step; anything we do to inhibit that process is dangerous to the mamma.

2.In addition to hats interfering with bonding and safety of third stage, hatting restricts the unmoulding of the baby’s skull. Plus the head is extremely sensitive in those first hours.

3.The hats we use in the U.S. do nothing for maintenance of core temp according to the studies I have found, and in fact one study showed that a hat was detrimental to maintenance of core temp. Brain cooling may actually be good for all babies and not those who have potential brain damage. And studies show that skin to skin with mom is most effective way to stabilize core temperature and that in fact, her body will heat and cool as
needed for baby’s sake as it did when baby was inside. Even if separated from mom, a hat is NOT proven to stabilize core temp unless it is woolen these stockinette or cotton hats we use are useless if not dangerous throw them away.

Brilliant! We cannot improve on this design. Why do we keep trying?

I hope you learned. I sure did, when I first heard of this concept. It’s a part of
protecting moms and protecting babies.