Etiology and risk factors
The development of the condition is directly linked to diseases and conditions that directly or indirectly impair the normal movement of the fertilized ovum through the fallopian tubes. Several main groups of causes are distinguished:
- Inflammatory diseases of the uterine appendages. This is the leading cause, ranking first. A history of acute salpingitis promotes adhesion formation and narrowing of the fallopian tube lumen. As a result, the risk of ectopic implantation increases 6–7 times compared to the healthy population.
- Hypoplasia of the corpus luteum of the ovary. Detected in nearly half of the cases, often combined with pre-existing structural pathology of the fallopian tubes.
- Iatrogenic factors. The risk increases significantly after reconstructive plastic surgery on the fallopian tubes (the probability rises to 6–27% depending on the type of surgical intervention). Ovulation induction in the treatment of endocrine infertility or in vitro fertilization (IVF) can also act as a trigger, increasing the risk up to 10%.
- Embryonic factor. If the trophoblast develops and differentiates too rapidly, it causes premature implantation of the blastocyst before it reaches the uterus.
- Rare causes. Include uterine malformations, the use of intrauterine devices (IUDs), and certain types of hormonal contraception.
Outcomes of tubal pregnancy
Since fallopian tubes account for up to 99% of all cases, their pathology is the most thoroughly studied. Due to the embryo invading a thin wall not intended for placentation, the pregnancy is terminated. This occurs in two ways:
- Rupture of the fallopian tube. The ovum literally bursts through the tissues and enters the abdominal cavity. Clinically, this manifests as sharp abdominal pain, dizziness, and signs of collapse caused by massive internal bleeding. This is a critical condition requiring emergency surgery.
- Tubal abortion. In this case, the ovum detaches from the tubal wall and is expelled into the abdominal cavity due to antiperistaltic contractions. If the embryo, placenta, and blood clots are retained in the lumen of the fallopian tube, it is referred to as an incomplete tubal abortion.
Abdominal pregnancy
This is an extremely severe condition with a poor prognosis. There is a constant threat to the mother of rupture of the gestational sac and fatal hemorrhage, while the fetus inevitably dies under such conditions. Patient survival is possible only in rare cases when internal bleeding does not become catastrophic.
Abdominal pregnancy is classified into two forms:
- Primary: an absolute rarity. Characterized by initial implantation of the ovum directly on abdominal organs (peritoneum, omentum, liver, spleen, or stomach).
- Secondary: somewhat more common. Arises as a direct consequence of tubal abortion or tubal rupture, when a viable ovum falls into the abdominal cavity and implants there secondarily.
Pathomorphology of ectopic pregnancy
Morphological diagnosis of tubal pregnancy usually presents no difficulty for the pathologist.
- Macroscopic appearance: the extracted fallopian tube appears locally dilated in a specific area. Upon opening, an ovum surrounded by blood clots (massive hemorrhage) is visualized within the lumen.
- Microscopic appearance: standard histological examination (hematoxylin and eosin staining) reveals extensive hemorrhages in the wall of the fallopian tube, along with clearly defined chorionic elements—trophoblast cells invading the underlying tissues.
Examination of uterine cavity material (differential diagnosis)
To confirm the localization of pregnancy or establish the fact of spontaneous uterine abortion, a histological examination of material obtained from uterine curettage is performed.
In most cases, intact embryos are not preserved, and only fragments of decidual tissue and chorionic villi are submitted for analysis. In uterine pregnancy termination, microscopic examination reveals:
- Foci of decidual tissue necrosis with prominent neutrophil infiltration.
- Thrombi in decidual blood vessels.
- Foci of hemorrhage of varying volume.
- Edematous chorionic villi lacking their own blood vessels (avascular).
Important: the goals of such a study are to prove the fact of pregnancy, estimate the approximate gestational age of the abortion based on villous structure, and rule out trophoblastic disease. If only decidual tissue without chorionic villi is found in the scraping, it may indirectly indicate the presence of an ectopic pregnancy.
Briefly: answers to topical questions
In which anatomical segments of the fallopian tube can the ovum localize during a tubal pregnancy?
In a tubal pregnancy, the ovum can localize in four anatomical segments of the fallopian tube. The following variants are distinguished based on localization within the tube:
- Ampullary segment — the most frequent localization of the ovum.
- Isthmic segment — occurs significantly less frequently.
- Interstitial segment — also refers to rare localizations.
- Fimbrial segment — distinguished in the clinical classification of ectopic pregnancy.
What rare forms of ectopic pregnancy are distinguished by localization, aside from tubal, ovarian, cervical, and abdominal?
In addition to the main forms, the following rare variants of ectopic pregnancy are distinguished:
- Pregnancy in a rudimentary uterine horn — associated with uterine malformations.
- Mural (intramural) pregnancy.
- Intraligamentary pregnancy.
- Cesarean scar pregnancy — occurs with a frequency of 1/1800 to 1/2500 performed cesarean sections.
- Pregnancy in the stump of a previously removed fallopian tube.
- Heterotopic pregnancy — coexistence of intrauterine and tubal pregnancy.
Multiple ectopic pregnancy and bilateral tubal pregnancy are also distinguished.
For quick memorization of causes, use the acronym VGIE: V — Inflammation (salpingitis), G — Hypoplasia (corpus luteum), I — Interventions (IVF, tubal plasty), E — Embryonic factor (early maturation of the trophoblast).
Class and exam questions
Where is ectopic pregnancy most commonly localized?
In 95–99% of cases, the fertilized ovum implants in the fallopian tubes. Extremely rarely, it occurs in the ovaries, abdominal cavity, or cervix.
How does a tubal abortion differ from a fallopian tube rupture?
During a rupture, the tubal wall is destroyed by the growing ovum, producing acute clinical signs of collapse due to hemorrhage. In a tubal abortion, the ovum detaches and is pushed into the abdominal cavity by the antiperistaltic contractions of the tube itself.
What is secondary abdominal pregnancy?
This is a condition where the ovum initially developed in the fallopian tube, but after a tubal abortion or rupture, it fell into the abdominal cavity and implanted there anew on internal organs.
What else to study on this topic
- Structure and frequency of chromosomal aberrations in spontaneous abortions (Turner syndrome, trisomies).
- Impact of infectious factors (CMV, rubella virus, Toxoplasma) on early pregnancy loss.
- Maternal extragenital diseases as a factor in pregnancy loss (diabetes mellitus, systemic lupus erythematosus).
- Histological structure of chorionic villi in normal and aborted pregnancies.
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