What to Expect: Changes in Your Body. Pregnancy is different for every woman. Some women glow with good health and vitality during those first three months; others feel absolutely miserable. Here are some of the changes you might experience, what they mean, and which signs warrant a call to your doctor. Bleeding. About 25% of pregnant women experience slight bleeding during their first trimester. Early in the pregnancy, light spotting may be a sign that the fertilized embryo has implanted in the uterus. However, if you have significant bleeding, cramping, or sharp pain in your abdomen, call your doctor. These could be signs of a miscarriage or ectopic pregnancy (a pregnancy in which the embryo implants outside of the uterus). Breast tenderness. Sore breasts are one of the earliest signs of pregnancy.