During the first trimester, the uterus
begins to stretch gently to make room for the growing embryo. The baby
grows to a length of about 3 inches and a weight of I ounce by the end
of the third month. It is during this time that the vital organs— heart,
lungs, intestines, brain, eyes, ears, and skeleton—are formed.
The baby grows to a length of about
14 inches and a weight of 2 pounds during the second trimester. Movements
of the fetus, called "quickening," happen at around 20 weeks. The doctor
will be able to hear the baby's heartbeat. Bones are growing, arm and leg
joints are forming, and the baby's teeth are well started.
During the final trimester, the baby's
tissues and organs mature, and strength and weight are gained. The baby
also starts kicking and moving about. The uterus moves higher in the abdomen
until about the middle of the last month. The baby's head then begins to
drop into the pelvis in preparation for delivery.