According to the Pregnancy Corner, the signs of a 16-week belly are an increase in weight in the womb and potential back pains. The average weight gain at this point in the pregnancy is about five to ten pounds.
In addition, Baby Center explains that women who are 16-weeks pregnant begin to feel more settled in the pregnancy. Morning sickness begins to subside, women experience fewer mood swings, and there are continuing changes in the look and size of the breasts. The milk begins to produce causing the blood flow to increase and make the blood vessels more visible through the skin. Prenatal testing should begin during the second trimester, as the doctor can start to rule out any potential problems with the baby.