The second trimester begins at week 14 and ends at week 26. At 14 weeks, the immune system continue...
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The second trimester begins at week 14 and ends at week 26. At 14 weeks, the immune system continues to develop and external genitalia can be seen. At 16 weeks, respiration develops. At 18 weeks, the ears stick out of the head and by 20 weeks, downy hair covers the body. At 23 weeks, the fetus can respond to sounds. At 24 weeks, the fetus is able to suck and hear sounds. Eyebrows and eyelashes can be seen. The third trimester begins at 26 weeks and ends with labor. At 27 weeks, the lungs begin to simulate breathing movements. At 28 weeks, the fused eyelids open, and the eyes can sense light. The ability to smell begins. The fetus can suck and swallow. At 32 weeks, the skin is red and crinkled. Fat starts to be deposited to round out the fetus. At 34 weeks, if it hasn't already, the fetus begins the descent into the pelvis to prepare for delivery. At 35 weeks, the fingernails reach the end of the fingertips. At 36 weeks, more body fat has formed so the body is rounder and less wrinkly. At 37 weeks, the lungs are considered mature, and the baby is not considered premature if delivered. At 40 weeks, the normal gestation period ends.