Your body goes through a great deal of hormonal, physiological, and physical changes during pregnancy. The way you nourish your body during this process will affect your own health, as well as the health of your baby. By following some fairly easy nutrition guidelines, you can be on your way to a healthy pregnancy.
Many women are concerned about weight gain during pregnancy. Some women fear gaining too much weight, wondering if they will ever get back to their pre-pregnancy size; others feel they may not be gaining enough weight. A woman gains more weight than just the weight of the baby. In order to produce a healthy baby, your body requires extra fluids-extra water, blood, and amniotic fluid. During pregnancy you gain about 15 to 20 pounds in water alone. You can discuss with your provider the appropriate amount of weight for you to gain during your pregnancy.
Source: Health Line