Description

• Spontaneous abortion (miscarriage) is the separation of products of conception from the uterus prior to the potential for fetal survival outside the uterus, generally defined as expulsion from the uterus of an embryo or fetus weighing ≤500 g. A number of other related terms:
  • Threatened abortion: Vaginal bleeding in the first trimester of pregnancy
  • Inevitable abortion: Cervical dilatation, rupture of membranes, or expulsion of products of conception in the presence of vaginal bleeding
  • Complete abortion: Entire contents of uterus expelled
  • Incomplete abortion: Abortion with retained products of conception, generally placental tissue; more common after 12 weeks’ gestation
  • Early pregnancy failure: Nonviable pregnancy identified by ultrasound (anembryonic or without embryonic cardiac activity)
  • Induced abortion: Evacuation of uterine contents or products of conception medically or surgically
  • Septic abortion: A spontaneous or therapeutic abortion complicated by pelvic infection; common complication of illegally performed induced abortions
  • Recurrent abortion: 2 or more consecutive pregnancy losses at <15 weeks’ gestation
• Synonym(s): Miscarriage; Habitual abortion; Involuntary pregnancy loss:
  • Missed abortion and blighted ovum are older terms that do not represent the pathophysiology of the process.

Epidemiology

Predominant age: Increases with advancing age, especially >35 years; at age 40, the loss rate is twice that of age 20

• Threatened abortion (1st-trimester bleeding) occurs in 20–25% of clinical pregnancies.
• Between 10% and 15% of all clinically recognized pregnancies end in SAb, with 80% of these occurring within 12 weeks after last menstrual period (LMP).
• When both clinical and biochemical (β-hCG detected) pregnancies are considered, up to 50% of pregnancies end in spontaneous abortion.

Risk Factors

Most cases of spontaneous abortion occur in patients without identifiable risk factors; however, risk factors listed in order of importance include:

• Chromosomal abnormalities
• Advancing maternal age
• Uterine abnormalities
• Maternal chronic disease (diabetes mellitus, polycystic ovarian syndrome, obesity, systemic lupus erythematosus, hypertension, antiphospholipid antibodies, thyroid disease, renal disease)
• Other possible contributing factors include smoking, alcohol, infection, and luteal phase defect, although conclusive data are currently lacking.

Genetics
~50–65% of 1st-trimester spontaneous abortions have significant chromosomal anomalies, with 50% of these being autosomal trisomies and the remainder being triploidy, tetraploidy, or 45X monosomies.

General Prevention

• There is insufficient evidence to support use of aspirin and/or other anticoagulants, bed rest, hCG, immunotherapy, progestogens, uterine muscle relaxants, or vitamins for general prevention of SAb, before or after threatened abortion is diagnosed.
• By the time hemorrhage begins, 1/2 of pregnancies complicated by threatened abortion already have no fetal cardiac activity.
• Recurrent abortion: Women with a history of 3 or more prior SAbs may benefit from progestogens (OR 0.38, 95% CI 0.20–0.70) (1)[A].
• Antiphospholipid syndrome: The combination of unfractionated heparin and aspirin reduces risk of SAb in women with antiphospholipid antibodies and a history of recurrent abortion (RR 46%, 95% CI 0.29–0.71) (2)[A].

Etiology

• Chromosomal anomalies (50–65% of cases)
• Congenital anomalies
• Trauma
• Maternal factors: Uterine abnormalities, infection (toxoplasma, other viruses, rubella, cytomegalovirus, herpesvirus), maternal endocrine disorders, hypercoagulable state

History

• Consider any reproductive-age woman with vaginal bleeding to be pregnant until proven otherwise.
• Vaginal bleeding:
  • Characteristics (amount, color, consistency, associated symptoms), onset (abrupt or gradual), duration, intensity/quantity, and exacerbating/precipitating factors
  • Document LMP if known: Allows calculation of estimated gestational age if no ultrasound (US) documentation of intrauterine pregnancy (IUP)
• Abdominal pain/uterine cramping, as well as associated nausea/vomiting/syncope
• Rupture of membranes
• Passage of products of conception
• Prenatal course: Toxic or infectious exposures, family or personal history of genetic abnormalities, past history of ectopic pregnancy or spontaneous abortion, endocrine disease, autoimmune disorder, bleeding/clotting disorder

Physical Exam

• Orthostatic vital signs to estimate hemodynamic stability
• Abdominal exam for tenderness, guarding, rebound, bowel sounds (peritoneal signs more likely with ectopic pregnancy)
• Speculum exam for visual assessment of cervical dilation, blood, and products of conception; bimanual exam for uterine size/tenderness and presence of adnexal mass

Diagnostic Tests and Interpretation

• Quantitative human chorionic gonadotropin (hCG)
  • Particularly useful if IUP has not been documented by US
  • Serial quantitative serum hCG measurements can assess viability of the pregnancy. Serum hCG should rise at least 67% every 48 hours through 7 weeks after LMP. An inappropriate rise/plateau of hCG suggests abnormal IUP or possible ectopic pregnancy.
• CBC with differential
• Rh type
• Cultures: Gonorrhea/Chlamydia

• In the case of vaginal bleeding with no documented IUP, follow serum hCG levels weekly to zero.
• If levels plateau, consider ectopic pregnancy, retained products of conception, or gestational trophoblastic disease.

• US exam to evaluate fetal viability and to rule out ectopic pregnancy:
  • hCG >2,000 mIU/mL necessary to detect IUP via transvaginal US (TVUS), >6,500 mIU/mL for abdominal ultrasound
• TVUS criteria for nonviable intrauterine gestation: 5-mm fetal pole without cardiac activity or 16-mm gestational sac without a fetal pole
• Structures and timing: with TVUS, gestational sac of 2–3 mm generally seen by 4 weeks +1–3 days; yolk sac by 5 weeks; fetal pole with cardiac activity by 5.5–6 weeks

• If initial hCG level does not permit documentation of IUP by TVUS, follow serum hCG in 48 hours to document appropriate rise.
• Repeat US once hCG is at a level commensurate with visualization on US (see above).
• Provide patient with ectopic precautions in interim: worsening abdominal pain, dizziness/syncope, nausea/vomiting.

• Fetal heart tones can be auscultated with Doppler starting between 10 and 12 weeks' gestation in a viable pregnancy.
• In threatened abortion, fetal cardiac activity at 7–11 weeks' gestation is 90–96% predictive of continued pregnancy.

Pathological Findings
Products of conception, placental villi

Differential Diagnosis

• Ectopic pregnancy: Potentially life-threatening; must be considered in any woman of childbearing age with abdominal pain and vaginal bleeding
• Physiologic bleeding in normal pregnancy (implantation bleeding)
• Cervical polyps, neoplasia, and/or inflammatory conditions
• Hydatidiform mole pregnancy
• hCG-secreting ovarian tumor

Medication (Drugs)

• Long-term conception rate and pregnancy outcomes are similar for women who undergo medical or surgical evacuation.
• Postinfection rates are lower with medical vs. surgical management.

• Misoprostol: Most common agent for inducing passage of tissue in missed or incomplete abortion:
  • Not approved by the FDA for treatment of early pregnancy failure
  • Efficacy: complete expulsion of products of conception in 71% by day 3, 84% by day 8
  • Efficacy depends on route of administration, gestational age of pregnancy, and dose.
  • Recommended dose is 800 μg vaginally (3)[A]; alternate regimens include the World Health Organization (WHO) regimen of 600 μg sublingually q3h for up to 3 doses; multidose regimens and oral dosing (including buccal and sublingual) may result in increased side effects. Concerns related to possible increased risk for C. sordelii infection with vaginal route are unproven but many protocols have switched to buccal route as a result.
• Common adverse effects include abdominal pain/cramping, nausea, and diarrhea. Pain increases at higher doses but is manageable with oral analgesia. There is no increase in nausea/diarrhea with a higher dose.
• Recommended for stable patients who decline surgery but do not want to wait for spontaneous passage of products of conception

Second Line
Rh-negative patients should be given Rh immunoglobulin (RhoGAM) following a spontaneous abortion.

Additional Treatment

General Measures
Discuss contraception plan at the time of diagnosis of SAb, as ovulation can occur prior to resumption of normal menses.

Issue for Referral
Patients should be monitored for up to 1 year for the development of pathological grief. There is insufficient evidence to indicate that counseling prevents development of anxiety or depression related to grief following SAb.

Complementary and Alternative Therapies

A systematic review of Chinese herbal medicine alone and in conjunction with Western medicine showed benefit over Western medicine alone in achieving continued viability at 28 weeks (NNT = 4.8 pregnancies with combined therapy) (4)[A]. However, the available studies did not meet international standards for reporting quality.

Surgery/Other Procedures

• Uterine aspiration (suction dilation and curettage (D&C) or manual vacuum aspiration) is the conventional treatment.
• Indications: Septic abortion, heavy bleeding, hypotension, patient choice
• Risks: Anesthesia (usually local), uterine perforation, intrauterine adhesions, cervical trauma, infection that may lead to infertility or increased risk of ectopic pregnancy
• When compared with expectant management, surgical intervention leads to fewer days of vaginal bleeding, with a lower risk of incomplete abortion and heavy bleeding, but a higher risk of infection (5)[A].
• Vacuum aspiration (manual or electric) is considered preferable to sharp curettage as aspiration is less painful, takes less time, involves less blood loss, and does not require general anesthesia (6)[A]. The WHO supports use of suction curettage over rigid metal curettage (5)[A].
• Data from induced abortions suggest that antibiotic prophylaxis with doxycycline 100 mg b.i.d. substantially reduces postprocedure infection risk; however, data for incomplete abortions treated surgically are inconclusive (7)[A].
• For patients who desire contraception after completion of a spontaneous abortion, immediate insertion of an intrauterine device is both acceptable and safe.

In-Patient Considerations

Initial Stabilization
If the patient has orthostatic vital signs, initiate resuscitation with IV fluids and/or blood products if needed.

IV Fluids
Hemodynamically unstable patients may require intravenous fluids and/or blood products to maintain BP.

Follow-Up Recommendations

All patients should be seen in 2–6 weeks to monitor for resolution of bleeding, return of menses, and symptoms related to grief, as well as to review the contraception plan.

• Identification of products of conception within material expelled from the uterus or D&C specimen
• If abortion is complete, observe the patient for further bleeding
• Pelvic rest until 2 weeks after evacuation
• If spontaneous abortion occurs in setting of previously documented IUP and abortion is completed with resumption of normal menses, it is not necessary to check or follow serum hCG to 0.

Diet

NPO if patient is to undergo D&C

Patient Education

Patient pamphlet (no. AP090) available from the American College of Obstetricians and Gynecologists, 409 12th St., SW, Washington, DC 20090-6290; (800) 762-2264 or online at http://www.acog.org

Prognosis

• Prognosis is excellent once bleeding is controlled.
• Recurrent abortion: Prognosis depends on etiology. Up to 70% rate of success with subsequent pregnancy.

Complications

• D&C: Uterine perforation, bleeding, adhesions, cervical trauma, and infection that may lead to infertility or increased risk of ectopic pregnancy
• Retained products of conception

See Also

• Ectopic Pregnancy
• Algorithm: Abortion, Recurrent

ICD-9

• 634.90 Spontaneous abortion, without mention of complication, unspecified
• 634.91 Spontaneous abortion, without mention of complication, incomplete
• 634.92 Spontaneous abortion, without mention of complication, complete
• 632 Missed abortion
• 637.00 Unspecified abortion, complicated by genital tract and pelvic infection, unspecified
• 637.90 Unspecified abortion, without mention of complication, unspecified
• 640.03 Threatened abortion, antepartum condition or complication

ICD-10

• O03.9 Complete or unspecified spontaneous abortion without complication
• O03.4 Incomplete spontaneous abortion without complication
• O02.1 Missed abortion
• O20.0 Threatened abortion
• N96 Recurrent pregnancy loss

SNOMED

• 17369002 Spontaneous abortion (disorder)
• 16607004 Missed abortion (disorder)
• 54048003 Threatened abortion (disorder)