I think that birth is SUPPOSED to be pretty traumatic for babies, so I'm not sure I buy into that. Babies are made to bend in strange ways so that they can fit through the birth canal. I can't imagine that it's particularly pleasant to have your skull be in multiple pieces so it can squish together and make it out of Mom. And don't forget that going through the birth canal is supposed to be a REALLY tight fit, and one of the frequent complications with C sections is that the baby doesn't get all the fluid squeezed out of her. I mean, when you're saying that it's a GOOD thing that the baby is squeezed so tightly that her lungs are completely compressed and anything in them has to come out, you're definitely not talking "fun times." Then there are mom hormones and baby hormones designed to race through them, and that can't be entirely pleasant.
If any of us, as adults, recreated a birth experience we'd most likely end up dead!
I think that births can range from easy to traumatic for Mom... but I kind of have the feeling that as far as the baby is concerned, birth ranges from traumatic to very traumatic. Luckily, they have very, very short memories!
I don't buy into this theory at all.