Comprehensive Clinical Study Notes on Ectopic Pregnancy

Definition and Comparative Risks of Ectopic Pregnancy

• Fundamentals of Implantation: The blastocyst normally implants in the endometrial lining of the uterine cavity. Any implantation occurring outside this location is defined as an ectopic pregnancy.

• Prevalence in Oviducts: More than $95\%$ of ectopic pregnancies involve the oviduct. However, the term "tubal pregnancy" is not synonymous with "ectopic gestation," as other sites exist.

• Mortality and Risks:

  • The risk of death from an extrauterine pregnancy is $10$ times greater than that for a vaginal delivery.

  • The risk of death is $50$ times greater than that for an induced abortion.

• Future Prognosis: The prognosis for a successful subsequent pregnancy is significantly reduced in women who have experienced an ectopic pregnancy, particularly if they are primigravid and over the age of $30$.

Etiology: Mechanical and Functional Factors

• Mechanical Factors: These factors prevent or retard the passage of the fertilized ovum into the uterine cavity:

  • Salpingitis: Specifically endosalpingitis, which causes agglutination of the arborescent folds of the tubal mucosa. This leads to narrowing of the lumen or the formation of blind pockets.

  • Peritubal Adhesions: Occur subsequent to postabortal or puerperal infections, appendicitis, or endometriosis. These adhesions can cause kinking of the tube and narrowing of the lumen.

  • Developmental Abnormalities: Includes diverticula, accessory ostia, and hypoplasia. These are rare but may occur following in utero exposure to diethylstilbestrol (DES).

  • Previous History: A previous ectopic pregnancy increases the chance of another to $7\%$ to $15\%$.

  • Previous Tubal Operations: Operations to restore patency or failures in tubal sterilization.

  • Induced Abortions: Multiple previous induced abortions may increase risk. The risk remains unchanged after one abortion but doubles after two, likely due to small increases in salpingitis incidence.

  • Tumors: Uterine myomas and adnexal masses that distort the tube.

  • Note: Tubal pregnancies are not increased by abnormal embryos.

• Functional Factors: These delay the passage of the ovum:

  • External Migration: This is generally not considered an important factor except in cases of abnormal Mullerian development (e.g., a hemiuterus with a non-communicating rudimentary horn).

  • Menstrual Reflux: Suggestion exists but has little supporting evidence.

  • Altered Tubal Motility: May follow changes in serum levels of estrogens and progesterone. This is likely due to changes in the number and affinity of adrenergic receptors in uterine and tubal smooth muscle.

  • Cigarette Smoking: Smoking at the time of conception has been shown to increase the incidence of ectopic pregnancy.

Assisted Reproduction and Contraceptive Failure

• Assisted Reproduction (ART): Several forms increase incidence:

  • Tubal pregnancy increases following ovulation induction, gamete intrafallopian transfer (GIFT), and in vitro fertilization (IVF) with ovum transfer.

  • Heterotypic Pregnancy: Heterotypic tubal pregnancy is increased after IVF, embryo transfer, and ovulation induction. Heterotypic cervical pregnancy is similarly increased following IVF and embryo transfer.

  • Abdominal Pregnancy: Reported following GIFT and IVF with ovum transfer.

• Failed Contraception:

  • While any contraceptive decrease the total number of ectopic pregnancies (by preventing pregnancy overall), if a pregnancy does occur during failure, the risk of it being ectopic is higher for certain methods.

  • High-Risk Failure Modes: Tubal sterilization ($16\%$ to $50\%$ rate in case of failure), intrauterine devices (IUDs), and progestin-only ‘minipills’.

  • Hysterectomy Cases: Ectopic pregnancy may follow hysterectomy if a fertilized ovum was trapped in the oviduct during the procedure, or more rarely, if a fistula developed between the vagina and the severed end of the oviduct.

Epidemiology and Maternal Mortality

• Epidemiological Trends: There has been a marked increase in both the rate and absolute number of ectopic pregnancies in the USA over the past two decades.

• Calculation Methods:

  1. Females 15 to 44 years: The number of ectopic pregnancies per $10,000$ females in this age range.

  2. Live Births: The number of ectopic pregnancies per $1000$ live births.

  3. Reported Pregnancies: The number of ectopic pregnancies per $1000$ reported pregnancies (includes live births, legally induced abortions, and ectopic pregnancies).

• Data Accuracy Issues: Numerators may be low (as cases occur outside the 15-44 age bracket) and denominators for live birth rates are low because they exclude stillbirths.

• Race and Age: Incidence is higher in nonwhite women compared to white women. Race and increased age are at least additive factors. Potential reasons for racial disparity include less available healthcare and higher reported frequency of sexually transmitted diseases.

• Mortality Status: Ectopic pregnancy remains the second leading cause of maternal mortality in many countries.

Anatomical Sites and Pathological Progression

• Primary Sites:

  • Ampulla: Most frequent site ($80\%$).

  • Isthmus: Second most common ($10\%$).

  • Interstitial: Implantation in the segment of the tube penetrating the uterine wall; occurs in approximately $2\%$ to $3\%$ of cases.

  • Other: Fimbriated extremity, fimbria ovarica, cervical, and ovarian.

• Zygote Implantation: The ovum burrows through the epithelium into the muscular wall (the tube lacks a submucosa). Proliferating trophoblasts invade and erode the subjacent muscularis, opening maternal vessels and pouring blood into spaces within the trophoblast.

• Decidual Reaction: The tube does not form an extensive decidua. The tubal wall offers slight resistance to trophoblast invasion. The embryo is often absent or stunted.

• Uterine Changes: The uterus undergoes softening of the cervix and isthmus and increases in size. Endometrial conversion to decidua is variable. The presence of uterine decidua without trophoblast suggests ectopic pregnancy but is not absolute.

• Vaginal Bleeding: Originates from the uterus and is associated with the sloughing of uterine decidua after fetal death. Occasionally, the decidua is cast off intact as a "decidual cast."

Natural History: Abortion vs. Rupture

• Tubal Abortion:

  • Common in ampullary pregnancies.

  • Involves separation of the conceptus and extrusion through the fimbriated end into the peritoneal cavity.

  • If separation is complete, hemorrhage and symptoms may disappear.

• Tubal Rupture:

  • Invading products of conception rupture the oviduct. Common outcome for isthmic pregnancies.

  • Timing: Early rupture (first few weeks) usually occurs in the isthmic portion. Interstitial rupture occurs later ($8^{\text{th}}$ to $11^{\text{th}}$ week).

  • Causes: May be spontaneous or triggered by trauma (coitus, bimanual exam).

  • Consequences: Profuse hemorrhage, signs of collapse/hypovolemia. Uncommonly, an expelled conceptus may reimplant (secondary abdominal pregnancy) or remain as an encapsulated mass (lithopedion).

Specific Ectopic Classifications

• Interstitial (Cornual) Pregnancy: About $3\%$ of tubal gestations. Diagnosis is often missed as no adnexal mass is felt; instead, uterine asymmetry occurs. Rupture later ($8-11$ weeks) can be rapidly fatal because it is located between the ovarian and uterine arteries.

• Heterotypic Ectopic Pregnancy: Coexisting intrauterine and extrauterine gestation. Historically $1$ per $30,000$ pregnancies but now more common. Significant signs: ART use, rising $\beta$-hCG after D&C, fundus larger than dates, presence of more than one corpus luteum, or ultrasound evidence of dual sites.

• Multifetal Ectopic: Twins in the same tube or one in each tube. Single-ovum twins are proportionally more common in tubal pregnancies than uterine.

• Tubo-Uterine: Extension from the interstitial portion into the uterine cavity.

• Tubo-Abdominal: Extension from the fimbriated end into the peritoneal cavity.

• Tubo-Ovarian: Fetal sac is adherent to both tubal and ovarian tissue.

Clinical Signs and Symptoms

• Classical Triad: Pelvic/abdominal pain ($3/4$ of cases), amenorrhea ($3/4$ of cases), and vaginal spotting/bleeding.

• Pain Characteristics: Sharp, stabbing, or tearing. Tenderness on abdominal palpation and exquisite pain upon motion of the cervix during virginal examination.

• Referred Pain: Symptoms of diaphragmatic irritation (pain in the neck or shoulder on inspiration) represent sizable intraperitoneal hemorrhage in $50\%$ of cases.

• Vasomotor Disturbances: Vertigo, syncope, and hypotension (often orthostatic).

• Uterine Size: In $1/4$ of cases, the uterus grows to nearly the same size as an intrauterine pregnancy during the first $3$ months.

• Temperature: Normal or low after acute hemorrhage; may rise to $38^{\circ}\text{C}$. Higher temperatures suggest infection.

• Pelvic Hematocele: Slow leakage of blood that is walled off by adhesions in the pelvis.

Laboratory and Diagnostic Tools

• Hemoglobin/Hematocrit: May initially show only slight reduction after hemorrhage due to the time required for hemodilution.

• Leukocyte Count: Normal in half of patients; may reach $30,000/\text{ml}$ in others.

• $\beta$-hCG Assays:

  • Urine: Latex agglutination inhibition slide tests (sensitivity $500$ to $800\,\text{mIU/ml}$). May yield false negatives due to low sensitivity.

  • Serum: Radioimmunoassay is the most precise method to confirm pregnancy.

• Sonography:

  • Abdominal: Difficult to identify tubal products. Absence of intrauterine sac + abnormal mass makes ectopic likely.

  • Vaginal: More sensitive and specific. Allows operator to exclude ovarian cysts/endometriomas.

• Culdocentesis: Simple technique to identify hemoperitoneum. Aspirated fluid containing old clots or non-clotting blood is compatible with ectopic pregnancy.

• Curettage: Used to differentiate from incomplete abortion. Probability of ectopic is high if no embryo/placenta is found and serum progesterone is < $5\,\text{ng/ml}$ or $\beta$-hCG is rising abnormally (< $2000\,\text{mU/mL}$).

• Laparoscopy: Provides visual diagnosis, though visualization may be hindered by active bleeding or inflammation.

Differential Diagnosis

• Gastrointestinal Disturbance: Symptoms like diarrhea, nausea, and vomiting can accompany rupture.

• Abortion of Intrauterine Pregnancy: In abortion, shock is proportional to vaginal blood loss; in ectopic pregnancy, shock is far in excess of visible blood loss.

• Ovarian Issues: Rupture of a corpus luteum or follicular cyst, or a twisted cyst.

• Appendicitis: Usually lacks signs of pregnancy or abnormal bleeding; mass is rarely found on vaginal exam.

• Intrauterine Devices: IUDs can cause cramping and bleeding, mimicking ectopic symptoms.

Management and Treatment

• General Goal: Preservation of the woman's life and, when possible, tubal conservation.

• Surgical Management:

  • Salpingectomy: Removal of the oviduct. Cornual resection (excising the outer third of the interstitial portion) is advised to minimize recurrence, but must not reach the uterine cavity to avoid future rupture risks.

  • Salpingostomy: For pregnancies < $2\,\text{cm}$ in the distal third of the tube. A linear incision is made on the antimesenteric border, and the ectopic is removed. Incision is left to heal by secondary intention.

• Medical Management (Methotrexate):

  • Criteria for Success: Gestation < $6$ weeks, tubal mass $\leq 3.5\,\text{cm}$, and no live fetus.

  • Patient Requirements: Hemodynamically stable, normal liver/renal function, normal hemogram.

  • Patient Compliance: Prohibition of sexual intercourse (until $\beta$-hCG is undetectable), alcohol, and multivitamins with folic acid.

  • Monitoring: Serial quantitative $\beta$-hCG titers (usually disappears within $14$ to $21$ days, occasionally $28$ days).

• Anti-D Immune Globulin: Administered to D-negative, non-sensitized patients to protect against isoimmunization.

Specialized Ectopic Forms

• Abdominal Pregnancy:

  • Etiology: Usually follows tubal rupture/abortion with secondary implantation on the serosa.

  • Diagnosis: MRI is the most accurate; CT is limited by radiation. Symptoms include abdominal discomfort and painful fetal movements.

  • Treatment: Surgery involves high risk of massive hemorrhage. At least $2000\,\text{ml}$ of compatible blood should be prepared.

• Ovarian Pregnancy: Defined by Spiegelberg criteria: intact tube on the affected side, fetal sac in the ovarian position, ovary connected to the uterus by the ovarian ligament, and ovarian tissue in the sac wall. Treated by wedge resection or cystectomy.

• Cervical Pregnancy: Trophoblast erodes the endocervix; duration depends on the site of implantation (higher implantation allows more growth/bleeding).

• Other Sites: Primary splenic pregnancy (identified by splenic rent and chorionic villi) and primary hepatic pregnancy (including cases of lithopedion).