Your body goes through many changes in the 4th, 5th and 6th months of pregnancy. For example, you will make a lot of blood. Your uterus (womb) and breasts grow larger. You will store extra body fat.
"SP441-B-Smart Choices...How Your Baby Grows - The Second Trimester," The University of Tennessee Agricultural Extension Service, , http://trace.tennessee.edu/utk_agexheal/64