During the second trimester your uterus will rapidly increase in size. At the end of this trimester the baby will be almost four times as big as it was at the end of the first trimester. Discomfort and outright pain come as a result of this growth process, as organs are pushed out of the way to make room for the uterus and as the muscles and support structures of the pelvis are stretched. The hormones that affect your body during pregnancy, such as progesterone, estrogen, and relaxin, also cause physical changes. Progesterone slows the digestive system, causing excess gas, constipation, and heartburn. Hormones also affect your skin, gums, and vision. Relaxin, the hormone that relaxes the pelvis to allow delivery, acts on other joints in your body, and may lead to lower back and foot pain.
It will help you throughout your pregnancy to learn methods for relieving these symptoms, while distinguishing between the normal discomforts of pregnancy and signs of a problem.