36 Weeks

From What to Expect:

Your baby's skull isn't the only soft structure in his or her little body. Most of your baby's bones and cartilage are quite soft as well (they'll harden over the first few years of life) — allowing for an easier journey as your baby squeezes through the birth canal at delivery (and less prodding and poking for Mom along the way). At 36 weeks pregnant, the skull bones are also not fused together yet so that the head can easily (well, relatively easily) maneuver through the birth canal.  

So your little bruiser (who you've now learned won't be bruising you all that much with those soft bones) is now about six pounds in weight and measures slightly more than 20 inches in length. Growth will experience a slowdown now, both so your baby will be able to fit the narrow passageway to the outside and also so he or she can store up all the energy needed for delivery.

By now, many of your baby's systems are pretty mature, at least in baby terms —  and just about ready for life on the outside. Blood circulation, for instance, has been perfected and your baby's immune system has matured enough to protect him or her from infections outside the womb. Other systems, however, still need a few finishing touches. Once such notable example: digestion — which actually won't be fully mature until sometime after birth. Why's that? Inside his or her little gestational cocoon, your baby has relied on the umbilical cord for nutrition, meaning that the digestive system — though developed — hasn't been operational. So your baby will take the first year or two to bring that system up to speed.

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