I heard most dolphins are born tail first. I have read many explanations from books and internet articles and they said that dolphins are born tail first to prevent them from drowning.
But now I don't get this explanation. There must be no air in the mother's womb, so the baby dolphin can't breathe either way. I think they get oxygen from the umbilical cord until it's disconnected.
If this is true, why would they drown if they are born head first? Why are dolphins born tail first unlike most mammals?