Causes of Ectopic Pregnancy
Ectopic pregnancy is primarily caused by factors that damage the fallopian tubes and alter embryo transport, with tubal damage from prior surgery or infection being the most significant risk factors. 1
Primary Causes
Tubal Damage
- History of tubal surgery (including sterilization) carries the highest risk 1
- Salpingitis (tubal infection) with resulting occlusion doubles the likelihood of ectopic pregnancy with each recurrent episode 1
- Previous ectopic pregnancy significantly increases risk due to surgical management or persistence of original risk factors 1
- Pelvic inflammatory disease (particularly from Chlamydia trachomatis infection) 2
Anatomical Considerations
- Over 97.7% of ectopic pregnancies occur in the fallopian tubes 3
- Distribution within the tube:
- Ampulla: approximately 80% of tubal pregnancies
- Isthmus: 12%
- Fimbria: 5% 3
- The right fallopian tube is more commonly affected (83.24% in one study) 3
Additional Risk Factors
- Cigarette smoking damages ciliary function in the fallopian tubes 2, 4
- In vitro fertilization and assisted reproduction 1, 2
- Previous abortion 3
- Intrauterine devices may alter tubal transport 5
- DES exposure (diethylstilbestrol) 5
Pathophysiological Mechanism
Ectopic pregnancy results from a combination of two key factors:
Impaired embryo-tubal transport: Damage to the fallopian tube prevents the fertilized egg from reaching the uterine cavity in a timely manner 2
Alterations in the tubal environment: Changes in the tubal lining allow for early implantation of the embryo outside the uterus 2
Clinical Implications
- Ectopic pregnancy accounts for 2% of reported pregnancies and 9% of pregnancy-related maternal deaths 1
- The classic presentation includes vaginal bleeding, abdominal pain, and amenorrhea 6
- Most ectopic pregnancies present as a nonspecific heterogeneous adnexal mass on ultrasound 6
- Prompt diagnosis is critical as rupture can lead to life-threatening hemorrhage
Diagnostic Considerations
- Transvaginal ultrasound is the primary imaging modality for evaluating suspected ectopic pregnancy 6
- A positive pregnancy test with empty uterus should raise suspicion 6
- Serial β-hCG measurements are essential when initial ultrasound is inconclusive 6
- The expected rise in viable intrauterine pregnancy is 53-66% over 48 hours 6
Prevention Strategies
- Early diagnosis and treatment of pelvic infections
- Smoking cessation
- Careful surgical technique during tubal procedures
- Close monitoring of pregnancies in women with risk factors
Understanding these causes is essential for early identification of at-risk patients and prompt intervention to reduce morbidity and mortality associated with ectopic pregnancy.