A baby fits through the birth canal by rotating and molding its head to navigate the shape of the pelvis.
During labor, as the baby descends, its head typically rotates so the back of its head is positioned just below the mother's pubic bone. This rotation helps the baby's head align with the widest parts of the pelvis. Most commonly, the baby will face down towards the mother's spine. However, sometimes the baby rotates to face upwards toward the pubic bone. The skull bones of a baby aren't fused, which allows the head to slightly change shape (mold) as it moves through the birth canal. This molding is a normal process that helps the baby fit.
In short, a baby "fits" through a combination of:
- Rotation: Turning to align with the widest diameter of the pelvic opening.
- Molding: Temporarily altering the shape of the skull.
