Why Human Babies Should Be Head Down Back Forward For Birth
Why Human Babies Are The Only Ones To Face The Mother’s Spine For Birth.
Because humans walk upright on two legs, their pelvis has been modified to support the trunk (body). Other placental creatures need the pelvis only for somewhere to attach the hind legs. Their babies have a straightforward path. They have their back to mother’s, and their front legs stretched forward, with their head and neck along their legs. First the toes emerge followed by the nose. There is a straight passage through the pelvis into the world. Even the great ape babies are born facing forward.
The human baby has a more complicated path. He is wider from front to back at the top of his head, and from side to side at his shoulders. When he has his back between his mother’s umbilicus and her left flank, he is able to curl forward and fold the bones of his skull along the joins (sutures) to make it smaller.
His mother’s pelvis is wider from side to side at the top. It has a basin in the middle, and is wider from front to back at the bottom. At the base of the lumber spine, we find a large, strong bone called the sacral prominence. This protrudes into the pelvic space and proves an obstacle to a baby who is not able to curl forward. The rest of the sacrum and coccyx plus the “spines” or side walls of the pelvis form a curved solid support for the body.
How will he fit through?
When his back is to the front, it is quite easy. He turns his head to face mother’s right groin, slides under the sacral prominence, curling tighter and turning until the top of his head is toward her spine as he goes. Now, he should have his shoulders just inside, and lying straight across the top of the pelvis. Once the uterine cervix is open, he moves down through the “spines”, the narrowest part of the pelvis, and brings his head into the world.
A turn to again face mother’s right thigh and his shoulders (posterior first) emerge followed by the rest of his body.
There will be no need for deliberate maternal pushing, as baby and uterus are able to manage his birth unaided.
Some second or later babies may prefer mother’s right side, but most of them choose her left.
What Should I Do?
During the last few weeks of pregnancy maternal posture becomes important if baby is to choose the best (optimal) position for birth. This is where Active Birth preparation belongs. Mother must try at all times to keep her knees and her abdomen apart. Her abdomen should always be lower than her spine. Yes, her back will sag—babies love the lordosis of pregnancy. She will have a bulgy “tummy” and walk with a “duck waddle” but it is only for a short time, and the results are worth it. Baby will be comfortable only in the optimal position.
A baby who has his back toward mothers, has a much more difficult journey. His back and neck are too straight, and he must bring his posterior shoulder past the sacral prominence before he can start to descend. He can’t really curl forward, because he is too close to mother’s pubic bone. Also, until labour is established–when the uterus tilts forward with each contraction, bringing his bottom forward—he will find it hard to enter the pelvis. Thus we get the typical backache labour.
His position means that mother’s nerves and hormones do not receive clear signals to start and continue the birth process.
We can discuss this topic in a later article.