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Spontaneous abortion
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Spontaneous abortion

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Contributors: Mitchell Linder MD
Other Resources UpToDate PubMed


A spontaneous abortion (SAB), or miscarriage, occurs when in early pregnancy, due to unknown reasons, the uterus undergoes the process of expelling its contents. A complete SAB is diagnosed when all of the uterine contents have been expelled. If anything remains in the uterus after initial assessment, those materials are referred to as retained products of conception, and the diagnosis is an incomplete abortion.

Approximately 10% percent of all pregnancies end in miscarriage, and about 80% of losses occur in the first trimester. Half of these losses will be related to fetal chromosomal abnormalities. A large number of losses will have an unexplained etiology.

Risk factors include increasing maternal age, history of prior uterine surgery, endocrine disease, history of prior pregnancy loss, short interval between pregnancies, radiation exposure, infections, genetic issues, autoimmune disease, and uterine abnormalities.

Patients may present with a variety of symptoms including pain / lower abdominal cramping, vaginal bleeding, and/or passage of blood clots or tissue.

Unfortunately, there are no interventions that truly protect against early loss.


003.9 – Complete or unspecified spontaneous abortion without complication

17369002 – Miscarriage

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

  • Threatened abortion – Vaginal bleeding but still viable fetus with cardiac activity seen on ultrasound.
  • Incomplete abortion – Retained products of conception remain after the initial bleeding / cramping have ceased.
  • Missed abortion – Usually diagnosed on ultrasound when there have been no outward symptoms of pregnancy loss; pregnancy tissue still in uterus but not progressing as expected.
  • Bleeding in early pregnancy – Will have viable pregnancy on ultrasound.
  • Ectopic pregnancy – Will not have the usual findings seen on ultrasound in early pregnancy.

Best Tests

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Management Pearls

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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Last Reviewed: 07/03/2018
Last Updated: 07/03/2018
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Spontaneous abortion
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Spontaneous abortion : Abdominal cramp, Low back pain, Pelvic pain, Heavy vaginal bleeding
Copyright © 2020 VisualDx®. All rights reserved.