An ectopic pregnancy occurs when the embryo never makes it to the uterus and starts to develop in the fallopian tube. If an ectopic pregnancy goes undetected, it strains the tube, which isn't designed to expand like the uterus. Then, 6-8 weeks after conception, the embryo will cause severe abdominal pain and possible vaginal bleeding. If the pain is more pronounced on one side, this is a textbook symptom of ectopic pregnancy.
Ectopic pregnancies are very dangerous.
If your tube ruptures, you could suffer severe internal bleeding, which is a life-threatening situation. Common symptoms of ectopic pregnancy are sharp abdominal cramps or pains on one side. The pains may start out as a dull ache that gets more severe with time. Neck pains and shoulder pains are also common. You may also have a menstrual type of bleeding along with the pain, but the pain is the most obvious sign.