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For further information, see CMDT Part 19-08: Spontaneous Abortion

Key Features

Essentials of Diagnosis

  • Intrauterine pregnancy < 20 weeks

  • Low or falling levels of human chorionic gonadotropin (hCG)

  • Bleeding or midline cramping pain, or both

  • Open cervical os

  • Complete or partial expulsion of products of conception

General Considerations

  • Defined as termination of gestation prior to the 20th week of pregnancy

  • 75% of cases occur before the 16th week, with 75% of these before the 8th week

  • Almost 20% of clinically recognized pregnancies terminate in spontaneous abortion

  • More than 60% of cases result from chromosomal defects

  • About 15% of cases are associated with

    • Maternal trauma

    • Infection

    • Dietary deficiency

    • Diabetes mellitus

    • Hypothyroidism

    • The lupus anticoagulant-anticardiolipin-antiphospholipid antibody syndrome

    • Anatomic malformations

    • There is no evidence that psychic stimuli such as severe fright, grief, anger, or anxiety can induce termination

  • There is no evidence that electromagnetic fields are associated with an increased risk of termination

  • It is important to distinguish women with incompetent cervix from more typical early abortion, premature labor, or rupture of the membranes


  • Predisposing factors

    • History of incompetent cervix

    • Cervical conization or surgery

    • Cervical injury

    • Diethylstilbestrol exposure

    • Anatomic abnormalities of the cervix

Clinical Findings

Symptoms and Signs

  • Incompetent cervix

    • Classically presents as "silent" cervical dilation (without contractions) between weeks 16 and 28

  • Threatened abortion

    • Bleeding or cramping without termination

    • The cervix is not dilated

  • Inevitable abortion

    • The cervix is dilated and membranes may be ruptured

    • Passage of products of conception has not occurred but is considered inevitable

  • Complete abortion

    • The products of conception are completely expelled

    • Pain ceases, but spotting may persist

    • Cervical os is closed

  • Incomplete abortion

    • Some portion of the products of conception remains in the uterus

    • Cramps are usually mild; bleeding is persistent and often excessive

  • Missed abortion

    • The pregnancy has ceased to develop, but the conception has not been expelled

    • There may be brownish vaginal discharge but no active bleeding

    • Symptoms of pregnancy disappear

Differential Diagnosis

  • Ectopic pregnancy

  • Hydatidiform mole

  • Incompetent cervix

  • Anovular bleeding in a nonpregnant women

  • Menses or menorrhagia

  • Cervical neoplasm or lesion


Laboratory Tests

  • Falling levels of hCG

  • Complete blood count should be obtained if bleeding is heavy

  • Rh type should be determined and Rho(D) Ig given if the type is Rh negative

  • All recovered tissue should be preserved and assessed by a pathologist

Imaging Studies

  • Transvaginal ultrasound can identify the gestational sac 5–6 weeks from the last menstrual period, a fetal pole at 6 weeks, and fetal cardiac activity at 6–7 weeks

  • Diagnostic criteria of early pregnancy loss

    • Crown-rump length of 7 mm or more and no heartbeat


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