From the Guidelines
The pathophysiology of ectopic pregnancy involves implantation of a fertilized egg outside the uterine cavity, most commonly in the fallopian tube, due to factors that impair embryo transport, allowing the blastocyst to implant in abnormal locations. This occurs due to factors that impair embryo transport through the fallopian tube, including anatomical tubal damage from previous pelvic inflammatory disease, prior surgery, endometriosis, or congenital abnormalities; functional impairment of tubal motility due to hormonal factors or smoking; and abnormal embryo development 1. The primary mechanisms of ectopic pregnancy can be understood by considering the definition of ectopic pregnancy as a pregnancy implanted in an abnormal location, whether intrauterine or extrauterine, as described in the American Journal of Obstetrics and Gynecology 1.
Some key points to consider in the pathophysiology of ectopic pregnancy include:
- Implantation of the fertilized egg outside the uterine cavity, most commonly in the fallopian tube
- Factors that impair embryo transport, such as anatomical tubal damage or functional impairment of tubal motility
- Abnormal embryo development
- The growing embryo causing distension of the affected structure, leading to pain
- The implantation site being unable to accommodate the growing embryo, resulting in rupture, hemorrhage, and potentially life-threatening bleeding
As the pregnancy progresses, the trophoblastic tissue invades the implantation site but lacks the normal decidualization response of the endometrium, contributing to the unstable nature of the implantation 1. Hormonal levels, particularly human chorionic gonadotropin (hCG), are typically lower than in normal pregnancies due to the suboptimal implantation environment, which is useful for diagnostic purposes. Early diagnosis and treatment are essential to prevent rupture and preserve fertility, and the location of the ectopic pregnancy should be specified, including tubal, interstitial, cervical, cesarean scar, ovarian, abdominal, and intramural locations, as recommended by the Society of Radiologists in Ultrasound consensus conference 1.
From the Research
Pathophysiology of Ectopic Pregnancy
The pathophysiology of ectopic pregnancy involves the implantation of a fertilized ovum outside of the uterine cavity, most commonly in the fallopian tube 2, 3. This can occur due to various risk factors, including:
- A history of pelvic inflammatory disease
- Cigarette smoking
- Fallopian tube surgery
- Previous ectopic pregnancy
- Infertility 2
Implantation and Development
The implantation of the fertilized ovum outside the uterine cavity can lead to the development of an ectopic pregnancy, which can cause symptoms such as vaginal bleeding and lower abdominal pain 2. The definitive diagnosis of ectopic pregnancy can be made with ultrasound visualization of a yolk sac and/or embryo in the adnexa, but most ectopic pregnancies do not reach this stage 2.
Diagnosis and Management
The diagnosis of ectopic pregnancy often relies on patient symptoms combined with serial ultrasonography and trends in beta human chorionic gonadotropin levels 2. Treatment options for diagnosed ectopic pregnancy include medical management with intramuscular methotrexate, surgical management via salpingostomy or salpingectomy, and expectant management in rare cases 2, 4, 5. In some cases, ectopic pregnancy can present late, even up to 19 weeks' gestation, and may require emergency laparotomy 6.
Risk Factors and Complications
Ectopic pregnancy is a significant cause of maternal mortality in the first trimester, and patients with a history of ectopic pregnancy have a poor prognosis for subsequent fertility 3, 4. Risk factors for ectopic pregnancy include pelvic inflammatory disease, previous pelvic or abdominal surgery, abnormal anatomy of genital organs, and assisted reproductive technologies 3, 6. Complications of ectopic pregnancy can include persistent ectopic pregnancy after salpingotomy, which can be treated with methotrexate 5.