The evolutionary solution to this problem turned out to be that as the size of the brain increased, hominid babies began to be born before their brains were fully developed. In fact, if you apply the normal rules of mammalian fetal development to humans, the “normal” gestation period for humans would be at least twelve months, not nine. But at twelve months the average infant brain would simply be too large to pass through the average human birth canal, making human birth mechanically impossible.
Females pelvic structure, even with anatomical evolutionary help, were not fit to give birth to a fully "mature" baby without the risk of dying. This was primarily due to the increased size of the brain but a interesting behavioral trait was lacking within the womb that our early ancestors and most primate species rely on to this day - as the birthing process is underway, infant apes will instinctively turn their heads to the side to ease the process... an instinct that no longer was passed down.
