Abortion, spontaneous




  • Separation of products of conception from the uterus prior to the potential for fetal survival outside the uterus
  • Spontaneous abortion (SAb):
    • Expulsion or extraction from the uterus of an embryo or fetus weighing ≤500 g
  • Threatened abortion:
    • Vaginal bleeding early in pregnancy without dilatation of the cervix, rupture of the membranes, or expulsion of products of conception
  • Inevitable abortion:
    • Cervical dilatation, rupture of membranes, or expulsion of products in the presence of vaginal bleeding
  • Complete abortion:
    • Entire contents of uterus expelled; common before 12 weeks’ gestation
  • Incomplete abortion:
    • Abortion with retained products of conception, generally placental tissue; more common after 12 weeks’ gestation
  • Missed abortion:
    • In utero death of embryo/fetus prior to 20 weeks’ gestation; products of conception retained
  • Induced abortion:
    • Evacuation of uterine contents or products of conception medically or surgically
  • Septic abortion:
    • Common complication of illegally performed induced abortions; a spontaneous or therapeutic abortion complicated by pelvic infection
  • Habitual spontaneous abortion:
    • 2 or more consecutive pregnancy losses at <15 weeks’ gestation
  • Synonym(s): Miscarriage; Habitual abortion; Recurrent abortion; Involuntary pregnancy loss

Epidemiologypills for miscarriage or spontaneous abortion - the end of a pregnancy

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


  • ∼8–20% of all clinically recognized pregnancies end in spontaneous abortion, 80% of these in the first 12 weeks.
  • When both clinical and biochemical (B-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, 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.


∼50–65% of 1st-trimester spontaneous abortions have significant chromosomal anomalies, with 1/2 of these being autosomal trisomies and the remainder being triploidy, tetraploidy, or 45X monosomies.

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General Prevention
  • Progestogens: Currently, there is no evidence that routine use of oral or IM progestogens prevents miscarriage in early to mid-pregnancy. However, there is some evidence that women with a history of recurrent miscarriage may benefit from this type of treatment (1)[A].
  • Immunotherapy: No current evidence to support use of immunotherapy in patients with a history of recurrent miscarriage (2)[A]


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



  • 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
  • Abdominal pain/uterine cramping
  • 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

  • Any pregnant woman with vaginal bleeding needs immediate evaluation.
  • Estimate hemodynamic stability:
    • Obtain orthostatic vital signs.
  • Abdominal exam for tenderness (SAb), guarding, rebound, bowel sounds (peritoneal signs more likely seen with ectopic pregnancy)
  • Pelvic exam for cervical dilation, blood, products of conception, uterine size/tenderness

Diagnostic Tests & Interpretation


Initial lab tests

  • Urine human chorionic gonadotropin (HCG)
  • Complete blood count
  • Rh type
  • Cultures: Gonorrhea/chlamydia
  • Serial serum HCG measurements can assess viability of the pregnancy. Serum HCG should rise at least 67% every 48 hours in early pregnancy.

Pregnancy Considerations

HCG levels are particularly useful in cases where an intrauterine pregnancy (IUP) has not been documented by ultrasound.

Follow-Up & Special Considerations
  • In the case of vaginal bleeding with no documented IUP, follow serum HCG levels weekly to zero to ensure complete expulsion of all products of conception.
  • If levels plateau, suspect ectopic pregnancy or retained products of conception.


Initial approach

  • Ultrasound (US) exam to evaluate fetal viability and to rule out ectopic pregnancy:
    • HCG >2,000 U/L necessary to detect IUP via transvaginal US (TVUS), >6,500 U/L for abdominal ultrasound
  • TVUS criteria for nonviable intrauterine gestation include 5-mm fetal pole without cardiac activity or 16-mm gestational sac without a fetal pole.

Follow-Up & Special Considerations

  • If initial HCG level does not permit documentation of IUP by TVUS, follow serum HCG in 48 hrs to ensure appropriate rise.
  • Follow HGC and repeat US once HCG at a level commensurate with visualization on US (see above).
  • Provide patient with ectopic precautions in interim.

Diagnostic Procedures/Surgery

  • Fetal heart tones can be auscultated with Doppler starting between 10–12 weeks’ gestation from last menstrual period for a viable pregnancy.
  • 90–96% of pregnancies with fetal cardiac activity and vaginal bleeding at 7–11 weeks’ gestation result in continued pregnancy.

Pathological Findings

Products of conception, placental villi

Differential Diagnosis

  • Ectopic pregnancy: Potentially life-threatening; must be ruled out with US in any woman of childbearing age with abdominal pain and vaginal bleeding
  • Cervical polyps, neoplasias, and/or inflammatory conditions can cause vaginal bleeding.
  • Hydatidiform mole pregnancy
  • HCG-secreting ovarian tumor
  • Physiologic bleeding in normal pregnancy (implantation bleeding)



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

First Line

  • Misoprostol: Most common agent for inducing passage of tissue in missed or incomplete abortion:
    • Not approved by Food and Drug Administration 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 800 µg vaginally (3)[A]; alternate regimens exist including World Health Organization regimen of 800 µg vaginally or 600 µg sublingually q.3 hours for up to 3 doses; multidose regimens and oral dosing may result in increased side effects
  • Common adverse effects include abdominal pain/cramping, nausea, and diarrhea. Pain increases at higher doses, but manageable with analgesia. No increase in nausea/diarrhea with 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 immune globulin following spontaneous abortion (4)[C].

Additional Treatment

General Measures
Explore any 1st-trimester vaginal bleeding.
Issues for Referral
Patients should be monitored for up to 1 year for the development of psychosomatic symptoms such as depression and anxiety (5)[A].
Complementary and Alternative Medicine
Vitamin supplementation does not appear to prevent miscarriage (6)[A].
Surgery/Other Procedures
  • Uterine aspiration (dilation and curettage or via vacuum aspiration) is the conventional treatment.
  • Indications: Septic abortion, heavy bleeding, hypotension, patient choice
  • Risks: Anesthesia, uterine perforation, intrauterine adhesions, cervical trauma, infection that may lead to infertility or increased risk of ectopic pregnancy
  • Surgical intervention leads to fewer days of vaginal bleeding, with a lower risk of incomplete abortion and heavy bleeding. It does carry a higher risk of infection (7)[A].
  • Vacuum aspiration may be less painful than dilatation and curettage (D & C), and does not require general anesthesia (8)[B].
  • Data from induced abortions suggests that antibiotic prophylaxis with doxycycline 100 mg b.i.d. substantially reduces postprocedure infection risk; however, data for incomplete abortions treated surgically is inconclusive (9)[A].
  • For patients who desire contraception after completion of a spontaneous abortion, immediate insertion of an intrauterine device is acceptable and safe (10)[A].

In-Patient Considerations

Initial Stabilization
If patient with orthostatic vital signs, initiate resuscitation with IV fluids and/or blood products if needed
IV Fluids
Hemodynamically unstable patients may require IV fluids and/or blood products to maintain blood pressure.

Ongoing Care

Follow-Up Recommendations

All patients should be seen in 2–6 weeks to monitor for resolution of bleeding, reestablishment of menses, review of contraception plan, and psychosomatic symptoms.

Patient Monitoring

  • Identification of products of conception within material expelled from the uterus or D & C specimen (important to distinguish villi and sac from decidua)
  • 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.


n.p.o. if patient to undergo dilation and curettage

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


  • If bleeding ceases, prognosis is excellent.
  • Habitual abortion:
    • Prognosis depends on etiology.
    • Prognosis is still excellent, with up to 70% rate of success with subsequent pregnancy.


  • Potential complications of D & C include uterine perforation, bleeding, adhesions, cervical trauma, infection that may lead to infertility, or increased risk of ectopic pregnancy.
  • Retained products of conception
  • Psychological morbidity, including depression, anxiety, feelings of guilt


1. Haas DM, Ramsey PS. Progestogen for preventing miscarriage. Cochrane Database Syst Rev. 2008;CD003511.
2. Porter TF, LaCoursiere Y, Scott JR. Immunotherapy for recurrent miscarriage. Cochrane Database Syst Rev. 2006;CD000112.
3. Neilson JP, Hickey M, Vazquez J. Medical treatment for early fetal death (less than 24 weeks). Cochrane Database Syst Rev. 2006;3:CD002253.
4. Prevention of Rho(D) alloimmunization. American College of Obstetricians and Gynecologists Practice Bulletin No 4. American College of Obstetricians and Gynecologists, Washington, DC: 1999.
5. Lok IH, Neugebauer R. Psychological morbidity following miscarriage. Best Pract Res Clin Obstet Gynaecol. 2007;21:229–47.
6. Rumbold A, Middleton P, Crowther CA. Vitamin supplementation for preventing miscarriage. Cochrane Database Syst Rev. 2005;CD004073.
7. Nanda K, Peloggia A, Grimes D et al. Expectant care versus surgical treatment for miscarriage. Cochrane Database Syst Rev. 2006;CD003518.
8. Forna F, et al. Surgical procedures to evacuate incomplete miscarriage. Cochrane Database Sys Rev. 2001;1:CD001993.
9. May W, Gülmezoglu AM, Ba-Thike K, et al. Antibiotics for incomplete abortion. Cochrane Database Syst Rev. 2007;CD001779.
10. Grimes DA, Lopez LM, Schulz KF, Van Vliet HA, Stanwood NL, et al. Immediate post-partum insertion of intrauterine devices. Cochrane Database Syst Rev. 2010;5:CD003036.
Additional Reading
Harwood B, et al. Quality of life and acceptability of medical vs. surgical management of early pregnancy. Br J Obstet and Gynaec. 2008;115(4):501–8.
12. Tam WH, Tsui MH, Lok IH et al. Long-term reproductive outcome subsequent to medical versus surgical treatment for miscarriage. Hum Reprod. 2005;20:3355–9.
13. Zhang J, Gilles JM, Barnhart K, Creinin MD, Westhoff C, Frederick MM, National Institute of Child Health Human Development (NICHD) Management of Early Pregnancy Failure Trial et al. A comparison of medical management with misoprostol and surgical management for early pregnancy failure. N Engl J Med. 2005;353:761–9.
See Also
Ectopic Pregnancy
Algorithm: Abortion, Recurrent



  • 632 Missed abortion
  • 634.90 Spontaneous abortion, unspecified, without mention of complication
  • 640.03 Threatened abortion, antepartum
  • 637.90 Legally unspecified type of abortion, unspecified, without mention of complication
  • 637.00 Unspecified type of abortion, unspecified, complicated by genital tract and pelvic infection
  • 17369002 Spontaneous abortion (disorder)
  • 16607004 Missed abortion (disorder)
  • 54048003 Threatened abortion (disorder)

Clinical Pearls

  • Any reproductive-age woman or pregnant woman with abdominal pain and vaginal bleeding must be evaluated. Ectopic pregnancy must be ruled out, and hemodynamic stability should be ensured.
  • Patient preference should determine whether management is medical, expectant, or surgical, as all options have similar long-term outcomes.
  • Assessment of psychological symptoms after spontaneous abortion should be an integral part of follow-up visits, with counseling, medication, and referral as appropriate.
  • Patients and their partners should be reassured that there are no known interventions to prevent spontaneous abortion, and should be provided with appropriate medical explanations to reduce anxiety and guilt.

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