Abortion, Spontaneous



  • Spontaneous termination of a <20 wk intrauterine pregnancy
  • Synonyms: Early pregnancy loss, miscarriage, early pregnancy failure
  • Occurs in up to 10–15% of recognized pregnancies (most common complication of early pregnancy):
    • ∼80% occur in first trimester
  • Vaginal bleeding in the first trimester is seen in about 25% of pregnant patients:
  • Definitions:
    • Threatened abortion: Vaginal bleeding, cervical os is closed, viable intrauterine pregnancy confirmed:
      • 50% of women seen in the ED for threatened abortion will eventually miscarry
    • Inevitable abortion: Vaginal bleeding, cervical os is open; products of conception (POC) have not been expelled
    • Incomplete abortion: Vaginal bleeding, cervical os is open with partial passage of some POC and some retained POC
    • Complete abortion: Vaginal bleeding, cervical os closed, complete passage of POC; no surgical or medical intervention
    • Missed abortion: Fetal demise with no uterine activity to expel
    • Septic abortion: Spontaneous abortion complicated by intrauterine infection
    • Recurrent spontaneous abortion: 3 or more consecutive pregnancy losses


  • Chromosomal abnormalities of the fetus
  • Uterine abnormalities (e.g., leiomyoma, uterine adhesions, congenital anomalies)
  • Risk factors include:
    • Increased age of both mother and father
    • Increased parity
    • Alcohol use
    • Cigarette smoking
    • Cocaine use
    • Conception within 3–6 mo after delivery
    • Chronic maternal disease:
      • Poorly controlled diabetes
      • Autoimmune disease
      • Celiac disease
    • Intrauterine device
    • Maternal BMI <18 or >25 kg/m2
    • Maternal infections:
      • Bacterial vaginosis
      • Mycoplasmosis
      • Herpes simplex
      • Toxoplasmosis
      • Listeriosis
      • Chlamydia/gonorrhea
      • HIV
      • Syphilis
      • Parvovirus B19
      • Malaria
      • CMV
      • Rubella
    • Medications:
      • Misoprostol
      • Methotrexate
      • NSAIDs
    • Multiple previous elective abortions
    • Previous early pregnancy loss
    • Toxins


Signs and Symptoms

  • Last menstrual period (LMP)
  • Obstetric history:
    • Parity
    • Risk factors for pregnancy loss
    • Prenatal care
  • Abdominal pain, cramping
  • Vaginal bleeding:
    • Duration
    • Amount of bleeding (quantify by number of pads used, compare with normal menstrual period for patient)
    • Passage of clots
  • Dizziness, syncope

Physical Exam
  • Determine hemodynamic status of patient:
    • Pregnant patients in late first trimester have an increased blood volume:
      • Can lose substantial amount of blood before having abnormal vital signs
  • Pelvic exam:
    • Determine whether the internal cervical os is open or closed
    • Amount of bleeding
    • Presence of POC
    • Presence of adnexal tenderness or peritoneal irritation can be consistent with an ectopic pregnancy
  • Bimanual exam to determine the size of the uterus:
    • Size of an orange: 6–8 wk
    • Fundus at the symphysis pubis: 12 wk
    • Fundus at the umbilicus: 16–20 wk

Essential Workup

  • Pregnancy test as below
  • Imaging as below

Diagnostic Tests and Interpretation

  • Confirm pregnancy with a urine or serum test:
    • Urine pregnancy test: Most are positive at β-hCG levels of 25–50 mIU/mL ∼1 wk gestational age and remain positive 2–3 wk after induced or spontaneous abortions
  • CBC
  • Type and Rh
  • Type and cross-match for woman with low Hct or signs of active blood loss
  • Quantitative β-hCG
  • Any POC passed should be sent to pathology for confirmation

  • Transvaginal ultrasound (TVS):
    • Gestational sac seen at 4 wk
    • Cardiac activity seen at 5.5 wk
  • Transabdominal ultrasound (TAS):
    • Gestational sac at 6 wk
    • Cardiac activity seen at 8 wk
  • Discriminatory zone: Level of β-hCG where a normal IUP should be detected:
    • 1,500–2,000 for TVS
    • 6,500 for TAS
  • Ultrasound findings consistent with early pregnancy loss:
    • Fetal crown–rump length of ≥7 mm and absent cardiac activity
    • Mean sac diameter of ≥25 mm without an embryo
    • Absence of an embryo with a cardiac activity ≥2 wk after a scan that showed a gestational sac without a yolk sac
    • Absence of an embryo with a cardiac activity ≥11 d after a scan that showed a gestational sac with a yolk sac

Differential Diagnosis

  • Positive pregnancy test with vaginal bleeding:
    • Cervicitis
    • Ectopic pregnancy
    • Molar pregnancy
    • Pregnancy of unknown location (PUL)
    • Septic abortions
    • Subchorionic hemorrhage
    • Trauma
  • Second- and third-trimester vaginal bleeding:
    • Placenta previa
    • Placental abruption


Pre Hospital

  • IV fluids, oxygen, and cardiac monitor
  • Monitor vital signs and transport
  • Caution:
    • Patients with spontaneous abortion/vaginal bleeding can have severe hemorrhage and present in shock, especially at >12 wk
    • BP drops during the second trimester of pregnancy with an average of 110/70

Initial Stabilization/Therapy

  • Stable patients:
    • IV
    • Pelvic exam
  • Unstable patients:
    • Oxygen, IV fluids via 2 large-bore IVs, cardiac monitor
    • Transfuse PRBC if patient does not stabilize after 2–3 L of crystalloid
    • Gynecologic consultation immediately
    • Oxytocin or methylergonovine may be necessary to control hemorrhage
    • These patients are at high risk for having ruptured ectopic pregnancies and may need emergent operative intervention

Ed Treatment/Procedures

  • Threatened abortion:
    • Pelvic rest, close follow-up with obstetrics
    • Patients <6.5-wk pregnant with no documented cardiac activity by vaginal US need to be followed with serial β-hCG to assess the viability of the fetus and to rule out ectopic pregnancy
  • Inevitable and incomplete abortions:
    • Expectant management:
      • Successful in up to 80%
      • Increased risk of unplanned surgical intervention and blood loss as compared to surgical management
    • Medical management:
      • Misoprostol
      • Successful in 80–93%
      • Reduces need for uterine curettage by up to 60%
      • Shortens time to completion
    • Surgical management:
      • Dilation and curettage (D&C) or evacuation, removal of POC at the cervical os to help decrease bleeding and cramping
      • Should be performed urgently in active hemorrhage, hemodynamic instability, or signs of infection
      • Reduces unplanned hospital admissions, curettages, and blood transfusions
      • Successful in 99%
      • The confirmation of POC by pathology rules out ectopic pregnancy
  • Complete abortion:
    • May treat with methylergonovine or oxytocin if bleeding is heavy
    • If quantitative β-hCG is <1,000 and the US is negative, may follow up with obstetrics for serial β-hCG to confirm the levels are decreasing
  • Missed abortion:
    • These patients are at risk for disseminated intravascular coagulation (DIC), especially if fetus is retained >4–6 wk
    • Obtain CBC, PT/PTT, fibrin-split products (FSP), and fibrinogen levels
    • These patients may be followed closely as outpatients if stable with an early, confirmed IUP and no evidence of DIC
    • Patients may choose to have a D&C at a later date or miscarry at home with medication or no intervention; this decision should be made in consultation with OB/GYN


First Line Medication:
  • RHO immunoglobulin in Rh-negative women:
    • 50 mcg for women with threatened or complete abortion at <12 wk
    • 300 mcg for women with threatened or complete abortion at ≥12 wk
  • Patients need RhoGAM administration within 72 hr to prevent future isoimmunization
  • Misoprostol 800 mcg vaginally if medical management is chosen in consultation with OB/GYN
    • Repeat dose in 48 hr as needed

Second Line Medication:
Usually given in consultation with OB/GYN:
  • Oxytocin: 20 units in 1,000 mL of NS at a rate of 20 milliunits/min titrated to decrease bleeding; may repeat for a max dose of 40 milliunits/min
  • Methylergonovine: 0.2 mg IM/PO QID for bleeding

Ongoing Care


Admission Criteria
  • Suspected unstable ectopic pregnancy (see “Ectopic Pregnancy”)
  • Hemodynamically unstable patients with hypovolemia or anemia
  • DIC
  • Septic abortions
  • Suspected gestational trophoblastic disease

Discharge Criteria
  • D&Cs/Evacuations can be done in the ED for incomplete and inevitable abortions, and patients may be discharged home if stable after 2–3 hr
  • Some early inevitable miscarriages can be discharged to complete their miscarriages at home without a D&C/Evacuation
  • Discharge with pain medications and close OB/GYN follow-up
  • Patients with threatened abortions should be told to avoid strenuous activity
  • Pelvic rest (i.e., “nothing in the vagina” during active bleeding; due to increased risk of infection)
  • Patients should be instructed to return to the ED for any increase in bleeding, dizziness, or temperature >100.4°F
  • Patients and their partners should be counseled that early pregnancy loss is common and that it is not anyone's fault

Follow-Up Recommendations

Patients with positive pregnancy tests and vaginal bleeding with or without abdominal pain should be followed by OB/GYN

Pearls and Pitfalls

  • Recognize the possibility of ectopic pregnancy
  • Patients with spontaneous abortion may have clinically significant blood loss

Additional Reading

  • Committee on Practice Bulletins—Gynecology. The American College of Obstetricians and Gynecologists Practice Bulletin no. 150. Early pregnancy loss. Obstet Gynecol. 2015;125:1258–1267.
  • Doubilet PM, Benson CB, Bourne T, et al. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med. 2013;369:1443–1451.
  • Huancahuari N. Emergencies in early pregnancy. Emerg Med Clin North Am. 2012;30:837–847.
  • Mazzariol FS, Roberts J, Oh SK, et al. Pearls and pitfalls in first-trimester obstetric sonography. Clin Imaging. 2015;39:176–185.
  • Sapra KJ, Joseph KS, Galea S, et al. Signs and symptoms of early pregnancy loss. Reprod Sci. 2017;24:502–513.
  • Tintinalli J, Stapczynki JS, Ma OJ, et al. Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 8th ed. New York: McGraw-Hill Education, 2016.

See Also


Ivette Motola
Patricia De Melo Panakos

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