I was reading that when babies are breech that there is most likely an abnormality with the baby because the babies biggest part of there body is the head so thats why it goes head down to get more room..
Babies are born head first because cervical pressure (pushing) through the birth canal as opposed to cervical pulling, is better for their body.
All mammals are born this way, and in wild animals, it's to reduce injury during birth since most animals are walking and avoiding predators within hours. A cervical injury from the weight of the body pulling on the neck as they're born could reduce their chances of survival even more.
So I don't think a baby's position has much to do with abnormalities, as much as with comfort and timing.