Good stuff..,

http://www.lamaze.org/ChildbirthEducators/ResourcesforEducators/CarePracticePapers/tabid/90/Default.aspx

Nature’s Plan for Birth
During the last weeks of pregnancy, your body and your baby prepare for birth. For a first-time mother, the baby often "drops down" into the pelvis in the weeks before birth. The cervix tilts forward and gradually begins to soften. Over a period lasting from a few days to a few weeks, you may (or may not) feel irregular contractions that help your cervix gradually thin and perhaps even dilate a few centimeters. During the last part of your pregnancy, your baby's lungs mature and he or she puts on a protective layer of fat, taking on the characteristic chubbiness of a newborn. Researchers now believe that when a baby is ready for life outside his mother's uterus, his body releases a tiny amount of a substance that signals the mother's hormones to begin labor.5 In most cases, your labor will begin only when both your body and your baby are ready.

A lot more great info in the articles.