What Causes Ectopic Pregnancy?

Extrauterine pregnancy—commonly known as ectopic pregnancy—is a potentially life-threatening condition in which a fertilized egg implants and begins to develop outside the uterine cavity. In over 95% of cases, implantation occurs in one of the fallopian tubes, though rare sites include the cervix, ovary, abdominal cavity, or cesarean scar. Early recognition is critical: untreated ectopic pregnancy can lead to tubal rupture, internal hemorrhage, and maternal mortality.

Several well-established risk factors contribute to the development of ectopic pregnancy. Pelvic inflammatory disease (PID), often caused by untreated chlamydial or gonococcal infection, induces tubal scarring and motility dysfunction—impairing normal embryo transport to the uterus. Prior tubal surgery—including sterilization reversal or salpingoplasty—alters tubal anatomy and increases adhesion formation. A history of previous ectopic pregnancy carries a 10–25% recurrence risk due to shared underlying pathology, such as chronic tubal damage.

Assisted reproductive technologies (ART), particularly in vitro fertilization (IVF), modestly elevate risk—not because of embryo transfer itself, but due to underlying infertility diagnoses like tubal factor infertility or endometriosis. Similarly, use of intrauterine devices (IUDs) or progestin-only contraceptives does not cause ectopic pregnancy but may fail to prevent ovulation or tubal transport; when pregnancy occurs despite these methods, the relative proportion of ectopic cases rises—even though absolute incidence remains low.

Other contributors include congenital tubal anomalies, endometriosis-related inflammation and adhesions, smoking (which disrupts ciliary function and tubal contractility), and advanced maternal age (>35 years). Emerging evidence also links certain assisted hatching techniques during IVF and elevated progesterone levels on the day of human chorionic gonadotropin (hCG) trigger to slightly increased risk—though causality remains under investigation.

It’s important to emphasize that many women with ectopic pregnancy have no identifiable risk factors. Therefore, clinicians must maintain a high index of suspicion in any woman of childbearing age presenting with pelvic pain, vaginal bleeding, or signs of hemodynamic instability—especially if serum β-hCG levels rise suboptimally or fail to double every 48 hours. Prompt ultrasound evaluation and serial biomarker monitoring are essential for timely diagnosis and intervention.