An ectopic pregnancy occurs when a fertilized egg is implanted outside the uterus, such as in a fallopian tube or the abdominal cavity, and therefore cannot develop normally. According to Dr. Erika Nichelson, an obstetrician/gynecologist with Mercy Medical Center in Baltimore, ectopic pregnancies initially cause the same symptoms as a typical pregnancy, such as a missed period or breast tenderness. “Because you are pregnant, the pregnancy hormone, hCG, is present, which is what gives you the symptoms of pregnancy. The pregnancy is not just in the uterus,” she explains. See a health care provider immediately if you have severe abdominal pain or vaginal bleeding while pregnant, as these are symptoms of ectopic pregnancy.