Going to the hospital involves catecholamines. No other animal in the world would give birth in such an impersonal, bacteria laden environment, full of strangers who the women dont know and who have no motivation to care for them. So your question about catecholamines postpartum has to take into consideration that the births you are talking about are births where the woman is a willing volunteer to a birth method that has been shown to increase maternal mortality- currently to 1 in 5000 women dying at hospital birth, and for no benefit, since planned hospital birth has no improvement on perinatal outcomes. So the women you are talking about are for all intents and purposes, suicidal at the point when they leave their homes to give birth in hospital. Suicidal because , 1 in every 5000 of them will die because of their choice to deliver in hospital. Sure they should have high catecholamines. Too bad the catecholamines are not high enough to push them to go home and deliver at a safe attended homebirth.