An ectopic pregnancy results when a fertilized egg implants outside the uterus. About 1 to 2 percent of pregnancies are ectopic. Because ectopic pregnancy is potentially dangerous for you, it’s important to recognize the early signs (such abdominal or pelvic pain, vaginal spotting, and shoulder pain) and get treatment as soon as possible.

https://www.babycenter.com/pregnancy/health-and-safety/ectopic-pregnancy_229