During the second trimester, your baby will go through many changes. In addition to the continued development of his major organs, his behavior will begin to change as well. Of course, he will continue growing and growing, and he will even likely begin to respond to your movements and sometimes voices.
During the first couple of weeks of the second trimester (weeks thirteen and fourteen) some interesting changes are going on. Your baby will begin to flex her little arms and legs, and even begin to kick, although you probably won’t feel it for some time. It is possible that she will even begin to put her thumb in her mouth. This is also the time that the meconium, the material that becomes your baby’s first bowel movement after she is born, begins to form. By the end of week fourteen, her mouth should be completely formed.
During the next few weeks of the second trimester, from about week 15 through week 19, your baby will go through more kinds of changes. He will be able to make a fist. His eyes will start to become sensitive to light. He will begin to make facial expressions. He will also begin to hear, and may by able to be startled or surprised by loud noises.
During the second half of the second trimester, even more changes occur to your baby. She will grow to about half a pound by your 20th week. By the 22nd week, she will weigh around one pound. Sometime during this period her lungs will start to begin inflating and deflating. She will develop her sense of balance during this time as well.
During the final weeks of your second trimester of pregnancy, your baby will go through yet more changes. He will weigh around 2 pounds. His hands will be fully formed. His eyebrows and eyelashes will have formed, as well. He won’t open his eyes for about two more weeks, however. If your baby makes it to week 27, the end of the 2nd trimester, his chance of survival is increased dramatically, as babies born at week 27 and after have an 85% chance of survival.