Your baby can now slide down a little further against the cervix and so that his head will rest against a layer of muscles traversing from one side of your pelvis to the other. These hammock-like muscles will telescope the front of his cranium, the frontal bone (Figure 7 and 8), and the back of his cranium, the occiput (Figure 9 and 10), beneath the two parietal bones. The stress fibers that form the dura mater will protect the blood vessels by restricting the amount of overlapping that can occur.

Figure 7: Frontal bone

Figure 8: The frontal plate telescopes under and/or over the adjacent parietal plate to reduce the size of the cranium and protect the brain.

Prolonged contact of your baby's head against the cervix is called engagement and it will stimulate the release of hormones from your placenta. It's still a mystery as to how the baby controls the hormone release, but I think simple biomechanics has a lot to do with it.

The hormone, oxytocin, will activate stronger contractions, which are more intense than the Braxton Hicks contractions. Oxytocin will also regulate your contractions into a rhythmical pattern. Your cervix will continue to soften and thin out as it blends in with the wider part of the uterus. Your baby's head can now rest directly against the opening called the os. Continued pressure against the os will start a cascade of hormonal responses in both you and your baby-this will lead to the active stage of labor and delivery.

Figure 9: The Occipital bone

Figure 10: The largest segment of the occipital bone telescopes under and/or over the adjacent parietal plates to further reduce the size of the cranium.