What Causes Ectopic Pregnancy?

Last Editorial Review: 1/11/2018

Ask the experts

I need to know how ectopic pregnancy occurs.  How does it happen or when?

Doctor's response

Ectopic pregnancy is pregnancy in a place other than in the womb (uterine cavity).  It usually takes 3 or 4 days for the fertilized egg to travel to the uterus from the fallopian tubes, and 3 more days for it to implant.  In ectopic pregnancy, something either blocks or holds up the process of the embryo traveling to where it needs to be, ie: implanted in the uterus.

The vast majority of cases of ectopic pregnancy are tubal pregnancies, where the pregnancy is in the fallopian tube.  Usually, this occurs because of a past pelvic inflammatory disease (PID).  About 5% of women who have PID will later develop ectopic pregnancy's sometimes years later.  Sometimes the woman will not even know she had a prior PID long ago and will be surprised to find this out.  The PID infection causes inflammation that can block the embryo from its required travel through the fallopian tube into the uterine cavity.  Known causes of ectopic pregnancy besides PID include endometriosis, prior ectopic pregnancy or tubal ligation, infertility, cigarette smoking, intrauterine device, and progesterone-based contraception, congenital abnormalities, diethylstilbestrol exposure.

Thank you for your question.

Medical Author: Carolyn Janet Crandall, M.D.


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