A female client is admitted to the emergency department complaining of severe right-sided abdominal pain and vaginal spotting. She states that her last menstrual period was about 2 months ago. A positive pregnancy test result and ultrasonography confirm an ectopic pregnancy. The nurse could best explain to the client that her condition is caused by:

The embryo itself may develop normally in the first several weeks of an ectopic pregnancy. An ectopic pregnancy in the fallopian tube causes severe pain owing to the size of the growing embryo within the narrow lumen of the tube, causing distention and finally rupture within the first 12 weeks of pregnancy. The Fallopian tube may either be normal or contain adhesions caused by a history of pelvic inflammatory disease or tubal surgeries, neither of which are congenital causes. An ectopic pregnancy does not involve a dysfunctional placenta, but the implantation of the blastocyst outside the uterus.