> Table of Contents > Abortion, Spontaneous (Miscarriage)
Abortion, Spontaneous (Miscarriage)
Clara M. Keegan, MD
image BASICS
  • Spontaneous abortion (SAb) (miscarriage) is the failure or loss of a pregnancy before 13 weeks' gestational age (WGA).
  • Related terms
    • Anembryonic gestation: gestational sac on ultrasound (US) without visible embryo after 6 WGA
    • Complete abortion: entire contents of uterus expelled
    • Ectopic pregnancy: pregnancy outside the uterus
    • Embryonic or fetal demise: cervix closed; embryo or fetus present in the uterus without cardiac activity.
    • Incomplete abortion: abortion with retained products of conception, generally placental tissue
    • Induced or therapeutic abortion: evacuation of uterine contents or products of conception medically or surgically
    • Inevitable abortion: cervical dilatation or rupture of membranes in the presence of vaginal bleeding
    • Recurrent abortion: ≥3 consecutive pregnancy losses at <15 WGA
    • Threatened abortion: vaginal bleeding in the 1st trimester of pregnancy
    • Septic abortion: a spontaneous or therapeutic abortion complicated by pelvic infection; common complication of illegally performed induced abortions
  • Synonym(s): miscarriage; early pregnancy loss
    • Missed abortion and blighted ovum are used less frequently in favor of terms representing the sonographic diagnosis.
Predominant age: increases with advancing age, especially >35 years; at age 40 years, the loss rate is twice that of age 20 years.
  • 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) (1).
  • When both clinical and biochemical (β-hCG detected) pregnancies are considered, about 30% of pregnancies end in SAb.
  • One in four women will have a SAb during her lifetime (1).
  • Chromosomal anomalies (50% of cases)
  • Congenital anomalies
  • Trauma
  • Maternal factors: uterine abnormalities, infection (toxoplasma, other viruses, rubella, cytomegalovirus, herpesvirus), maternal endocrine disorders, hypercoagulable state
Approximately 50% of 1st-trimester SAbs have significant chromosomal anomalies, with 50% of these being autosomal trisomies and the remainder being triploidy, tetraploidy, or 45X monosomies.
Most cases of SAb occur in patients without identifiable risk factors; however, risk factors include the following:
  • Chromosomal abnormalities
  • Advancing maternal age
  • Uterine abnormalities
  • Maternal chronic disease (antiphospholipid antibodies, uncontrolled diabetes mellitus, polycystic ovarian syndrome, obesity, hypertension, thyroid disease, renal disease)
  • Other possible contributing factors include smoking, alcohol, cocaine use, infection, and luteal phase defect.
  • Insufficient evidence supports the 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 prior SAbs may benefit from progestogens (OR 0.39, 95% CI 0.21-0.72) (2)[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 (RRR 46%, 95% CI 0.29-0.71) (3)[A].
  • 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 (confirms diagnosis of SAb)
  • Bimanual exam to assess for uterine size-dates discrepancy and adnexal tenderness or mass
  • 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)
  • Subchorionic bleeding
  • Cervical polyps, neoplasia, and/or inflammatory conditions
  • Hydatidiform mole pregnancy
  • hCG-secreting ovarian tumor
Initial Tests (lab, imaging)
  • Quantitative hCG
    • Particularly useful if intrauterine pregnancy (IUP) has not been documented by US.
    • Serial quantitative serum hCG measurements can assess viability of the pregnancy. Serum hCG should rise at least 53% every 48 hours through 7 weeks after LMP. An inappropriate rise, plateau, or decrease of hCG suggests abnormal IUP or possible ectopic pregnancy.
  • Complete blood count (CBC) with differential
  • Rh type
  • Cultures: gonorrhea/chlamydia
  • US exam to evaluate fetal viability and to rule out ectopic pregnancy (4)[A]
    • hCG >2,000 mIU/mL necessary to detect IUP via transvaginal US (TVUS), >5,500 mIU/mL for abdominal US
    • TVUS criteria for nonviable intrauterine gestation: 7-mm fetal pole without cardiac activity or 25-mm gestational sac without a fetal pole, IUP with no growth over 1 week, or previously seen IUP no longer visible
    • Structures and timing: with TVUS, gestational sac of 2 to 3 mm generally seen around 5 WGA; yolk sac by 5.5 WGA; fetal pole with cardiac activity by 6 WGA
Follow-Up Tests & Special Considerations
  • In the case of vaginal bleeding with no documented IUP and hCG <2,000 mIU/mL, follow serum hCG levels weekly to zero.
  • If levels plateau, consider ectopic pregnancy or retained products of conception. If levels are very high, consider gestational trophoblastic disease.
  • 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.
  • In a pregnancy of unknown location with hCG rise <53% in 48 hours, offer methotrexate for treatment of presumed ectopic pregnancy.
Diagnostic Procedures/Other
  • Fetal heart tones can be auscultated with Doppler starting between 10 and 12 WGA in a viable pregnancy.
  • In threatened abortion, fetal cardiac activity at 7 to 11 WGA is 90-96% predictive of continued pregnancy.
  • Discuss contraception plan at the time of diagnosis of SAb, as ovulation can occur prior to resumption of normal menses.
  • Expectant management (“watchful waiting”) is 90% effective for incomplete abortion, although it may take several weeks for the process to be complete (1)[A]. This approach is only recommended in the 1st trimester and is more effective in women with symptoms of impending pregnancy loss (5)[C].

  • Long-term conception rate and pregnancy outcomes are similar for women who undergo expectant management, medical treatment, or surgical evacuation.
  • Postinfection rates are lower with medical versus surgical management.
First Line
  • Misoprostol: most common agent for inducing passage of tissue in missed or incomplete abortion
    • Off-label use; has not been submitted to the FDA for consideration for use in treatment of early pregnancy failure. Recognized by the World Health Organization (WHO) as a life-saving medication for this indication.
    • 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; alternate regimens include the 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.
  • 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) 50 µg IM following a SAb.
  • Women with evidence of anemia should receive iron supplementation.
Patients should be monitored for up to 1 year for the development of pathologic grief. There is insufficient evidence to support counseling to prevent development of anxiety or depression related to grief following SAb.
  • Uterine aspiration (suction dilation and curettage [D&C] or manual vacuum aspiration [MVA]) is the conventional treatment.
  • Indications: septic abortion, heavy bleeding, hypotension, patient choice
  • Risks (all rare): 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 (6)[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. The WHO supports use of suction curettage over rigid metal curettage.
  • Although data from induced abortions suggest that antibiotic prophylaxis with doxycycline 100 mg BID reduces the already rare risk of postprocedure infection, data are insufficient to support use of antibiotics after aspiration for SAb (7)[A].
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 (number needed to treat [NNT] = 4.8 pregnancies with combined therapy). However, the available studies did not meet international standards for reporting quality (8)[C].
Admission Criteria/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 IV fluids and/or blood products to maintain BP.
All patients should be offered follow-up in 2 to 6 weeks to monitor for resolution of bleeding, return of menses, and symptoms related to grief, as well as to review the contraception plan.
Patient Monitoring
  • If SAb 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.
  • After medical management, confirm complete expulsion with US or serial serum β-hCG (5)[C].
  • If pregnancy is not immediately desired, offer effective contraception. Immediate insertion of an intrauterine device is both acceptable and safe.
  • If pregnancy is desired, provide preconception counseling. There is no evidence that it is necessary to wait a certain number of cycles before attempting conception again.
NPO if patient is to undergo D&C under general anesthesia
  • Pelvic rest for 1 week after D&C or MVA
  • Advise patients to call with excessive bleeding (soaking two pads per hour for 2 hours), fever, pelvic pain, or malaise, which could indicate retained products of conception or endometritis.
  • A patient fact sheet on miscarriage is available through the American Academy of Family Physicians at http://www.aafp.org/afp/2011/0701/p85.html.
  • Prognosis is excellent once bleeding is controlled.
  • Recurrent abortion: Prognosis depends on etiology; up to 70% rate of success with subsequent pregnancy
1. Prine LW, MacNaughton H. Office management of early pregnancy loss. Am Fam Physician. 2011;84(1):75-82.
2. Haas DM, Ramsey PS. Progestogen for preventing miscarriage. Cochrane Database Syst Rev. 2013;(10):CD003511.
3. Empson M, Lassere M, Craig J, et al. Prevention of recurrent miscarriage for women with anti-phospholipid antibody or lupus anticoagulant. Cochrane Database Syst Rev. 2005;(2):CD002859.
4. Doubilet PM, Benson CB, Bourne T, et al. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med. 2013;369(15): 1443-1451.
5. Committee on Practice Bulletins—Gynecology. The American College of Obstetricians and Gynecologists Practice Bulletin No. 150. Early pregnancy loss. Obstet Gynecol. 2015;125(5):1258-1267.
6. Nanda K, Lopez LM, Grimes DA, et al. Expectant care versus surgical treatment for miscarriage. Cochrane Database Syst Rev. 2012;(3):CD003518.
7. May W, Gülmezoglu AM, Ba-Thike K. Antibiotics for incomplete abortion. Cochrane Database Syst Rev. 2007;(4):CD001779.
8. Li L, Dou L, Leung PC, et al. Chinese herbal medicines for threatened miscarriage. Cochrane Database Syst Rev. 2012;(5):CD008510.
Additional Reading
  • Murphy FA, Lipp A, Powles DL. Follow-up for improving psychological well being for women after a miscarriage. Cochrane Database Syst Rev. 2012;(3):CD008679.
  • Neilson JP, Gyte GM, Hickey M, et al. Medical treatments for incomplete miscarriage. Cochrane Database Syst Rev. 2013;(3):CD007223.
  • Okusanya BO, Oduwole O, Effa EE. Immediate postabortal insertion of intrauterine devices. Cochrane Database Syst Rev. 2014;(7):CD001777.
  • Tunçalp O, Gülmezoglu AM, Souza JP. Surgical procedures for evacuating incomplete miscarriage. Cochrane Database Syst Rev. 2010;(9):CD001993.
See Also
  • Ectopic Pregnancy
  • Algorithm: Abortion, Recurrent
  • O03.9 Complete or unspecified spontaneous abortion without complication
  • O03.4 Incomplete spontaneous abortion without complication
  • O02.1 Missed abortion
Clinical Pearls
  • Any pregnant woman with abdominal pain and/or vaginal bleeding must be evaluated to rule out ectopic pregnancy, which is potentially life threatening.
  • As all options have similar long-term outcomes, patient preference should determine whether management is expectant, medical, or surgical.