Final answer:
During weeks 38-40 of pregnancy, the uterus drops and the abdomen transforms in shape as the fetus prepares to turn to a downward position before birth.
Step-by-step explanation:
During the last several weeks of the third trimester, the uterus continues to expand rapidly and takes up a larger portion of the woman's abdomen. By the end of week 38, the woman's abdomen often transforms in shape as it drops, relieving pressure on the upper abdomen but increasing pressure on the pelvic floor and rectum. This position of the uterus is preparing the body for the fetus to turn to a downward position before birth so its head rests on the cervix.