Pregnancy is a fascinating time of change for a new life growing within the womb. A baby grows a great deal from the point following conception to the time just prior to birth. Changes in appearance are also remarkable and a baby will grow from a being what resembles a human in the earliest weeks into a developed newborn ready for the world.
Identification
At conception, a baby begins as a group of cells that are rapidly multiplying and becoming bigger. These cells continue to form the organs and tissues of the body, and the baby's appearance changes as new body parts develop. During pregnancy, the most development occurs during the first trimester, or the first 12 weeks. The second and third trimesters are more about a baby's growth and weight gain rather than development of features.
First Trimester
The first trimester is the time of the largest number of changes for a baby. His arms and legs begin as buds and lengthen to develop fingers and toes. By eight weeks, a baby has all of the vital organs he needs for life, although they are not fully developed. According to the American Pregnancy Association, by the end of the first trimester, a baby is approximately 3 inches long, with almost half his size being his head.
Second Trimester
The second trimester occurs from the fourth through the sixth month of pregnancy. During this time, a mother begins to feel her baby kick as she becomes more active and her muscles contract. By the end of five months, a baby has eye lashes and eyebrows and hair on her head. By the end of the second trimester, a baby may be approximately 14 inches long and weigh almost 2 pounds.
Third Trimester
The third trimester begins at the 24th week and lasts until delivery at approximately 40 weeks. At 24 weeks, a baby looks like a smaller and thinner version of a full-term newborn. During the third trimester, he develops fingerprints and his lungs continue to mature throughout this phase of pregnancy. He develops a protective covering called vernix that is sticky and protects the skin, some of which may still be apparent after birth.
Labor
At the end of pregnancy, a baby has grown enough that she does not have as much room to move, and her arms and legs are flexed. As delivery approaches, most babies will move down into the mother's pelvis, signifying that labor is close. Most babies will present with their heads down in the pelvis, as delivery occurs head-first. Some babies turn and continue to grow with their feet or buttocks down, and this portion is what drops in the mother's pelvis. This is a breech presentation and typically requires delivery by cesarean section.
