Which of the following anatomic locations?

A 25-year-old female patient with a history of pelvic inflammatory disease (PID) presents for preconception counseling. She heard from a friend that she is at higher risk for an ectopic pregnancy due to her history of PID, and she is curious about where fertilization and implantation usually take place. You tell her that fertilization normally occurs in which of the following anatomic locations?

Ampulla of fallopian tube
Infundibulum of fallopian tube
Isthmus of fallopian tube
Isthmus of uterus

Correct answer
Ampulla of fallopian tube

correct answer: A

The correct answer is A. Fertilization normally occurs in the ampulla of the fallopian tube (Choice A), which is the longest and widest part. Less commonly, it occurs in the infundibulum of the fallopian tube (Choice B), which is the funnel-shaped termination formed of fimbriae. After fertilization, the ovum remains in the fallopian tube for approximately 72 hours before being swept down the fallopian tube by cilia into the uterine cavity, where it implants. PID is a risk factor for ectopic pregnancy, as it can lead to tubal scarring or decreased peristalsis which, in turn, can lead to abnormal implantation outside the uterine cavity. Fertilization does not normally occur in the isthmus of the fallopian tube (Choice C), isthmus of the uterus (Choice D), or the vagina (Choice E).