What are the risk factors for ectopic pregnancy?

Risk Factors for Ectopic Pregnancy

History of tubal surgery, including sterilization, carries the highest risk for ectopic pregnancy, followed by salpingitis (pelvic inflammatory disease) which doubles the risk with each recurrent episode. 1

Highest Risk Factors (Tubal Damage and Altered Embryo Transport)

The most critical risk factors are those that cause tubal damage and impair normal embryo transport through the fallopian tube 1:

Primary Risk Factors:

• Tubal surgery (including sterilization procedures) - represents the highest risk category 1
• Salpingitis/Pelvic inflammatory disease (PID) - risk doubles with each recurrent episode due to progressive tubal occlusion 1, 2
• Previous ectopic pregnancy - creates significant risk increase either from surgical management effects or persistence of original risk factors 1, 3
• Chlamydia trachomatis infection - a specific infectious cause of tubal damage 2

Assisted Reproductive Technology:

• In vitro fertilization (IVF) and induced ovulation have become increasingly important risk factors 1
• Critical caveat: Even with IVF, tubal factors (previous salpingitis, tubal surgery, prior ectopic pregnancy) remain the most important underlying risk factors 1
• Heterotopic pregnancy (simultaneous intrauterine and ectopic) increases with greater number of implanted embryos and ovarian stimulation 1
• No relationship exists between spontaneous versus stimulated ovulation, type of ovarian stimulation, or number of implanted embryos and ectopic pregnancy risk in isolation 1

Additional Established Risk Factors:

• Cigarette smoking 2, 3
• Endometriosis 2
• Age over 35 years 4
• History of infertility 3

Important Clinical Considerations

A significant number of patients with confirmed ectopic pregnancy will not have an identifiable risk factor 4, making it essential to maintain clinical suspicion in any woman of reproductive age presenting with early pregnancy symptoms, regardless of risk factor profile.

The American College of Emergency Physicians emphasizes that despite changes in epidemiology over recent decades, ectopic pregnancy remains the most common cause of maternal death and serious morbidity in the first trimester 1. This accounts for 9% of pregnancy-related maternal deaths in the United States 1.

Factors That May Have Reduced Recent Incidence:

• Earlier diagnosis of pelvic infections with more effective antibiotic therapy, potentially reducing tubal damage 1
• Increased medical (rather than surgical) management of early ectopic pregnancies, theoretically causing less tubal damage 1