Ectopic pregnancy is a complication of pregnancy in which the embryo attaches outside the uterus. Signs and symptoms classically include abdominal pain and vaginal bleeding, but fewer than 50 percent of affected women have both of these symptoms. The pain may be described as sharp, dull, or crampy. Pain may also spread to the shoulder if bleeding into the abdomen has occurred. Severe bleeding may result in a fast heart rate, fainting, or shock. With very rare exceptions the fetus is unable to survive.

Overall, ectopic pregnancies annually affect less than 2% of pregnancies worldwide. Risk factors for ectopic pregnancy include pelvic inflammatory disease, often due to chlamydia infection; tobacco smoking; prior tubal surgery; a history of infertility; and the use of assisted reproductive technology. Those who have previously had an ectopic pregnancy are at much higher risk of having another one. Most ectopic pregnancies (90%) occur in the fallopian tube, which are known as tubal pregnancies, but implantation can also occur on the cervix, ovaries, caesarean scar, or within the abdomen. Detection of ectopic pregnancy is typically by blood tests for human chorionic gonadotropin (hCG) and ultrasound. This may require testing on more than one occasion. Ultrasound works best when performed from within the vagina. Other causes of similar symptoms include: miscarriage, ovarian torsion, and acute appendicitis.

Prevention is by decreasing risk factors such as chlamydia infections through screening and treatment. While some ectopic pregnancies will miscarry without treatment, the standard treatment for ectopic pregnancy is an abortion. The use of the medication methotrexate works as well as surgery in some cases. Specifically it works well when the beta-HCG is low and the size of the ectopic is small. Surgery such as a salpingectomy is still typically recommended if the tube has ruptured, there is a fetal heartbeat, or the woman's vital signs are unstable. The surgery may be laparoscopic or through a larger incision, known as a laparotomy. Maternal morbidity and mortality are reduced with treatment.

The rate of ectopic pregnancy is about 11 to 20 per 1,000 live births in developed countries, though it may be as high as 4% among those using assisted reproductive technology. It is the most common cause of death among women during the first trimester at approximately 6-13% of the total. In the developed world outcomes have improved while in the developing world they often remain poor. The risk of death among those in the developed world is between 0.1 and 0.3 percent while in the developing world it is between one and three percent. The first known description of an ectopic pregnancy is by Al-Zahrawi in the 11th century. The word "ectopic" means "out of place".