eMedicine Specialties > Emergency Medicine > Obstetrics & Gynecology

Abortion, Threatened

Author: Slava V Gaufberg, MD, Assistant Professor of Medicine, Harvard Medical School; Director of Transitional Residency Training Program, Cambridge Health Alliance
Contributor Information and Disclosures

Updated: Dec 17, 2008

Introduction

Background

An abortion is the spontaneous or induced loss of early pregnancy. Early pregnancy is considered any pregnancy less than 20 weeks of gestation, defined by the inability of the fetus to survive outside of the uterus. The term miscarriage is often used to denote spontaneous abortion.

Pathophysiology

A spontaneous abortion is a process that can be divided into 4 stages, as follows: threatened, inevitable, incomplete, and complete.

• Threatened abortion: Vaginal bleeding of any degree during early pregnancy is considered to represent a threatened abortion, although such bleeding is very common. Approximately a fourth of all pregnant women have some degree of vaginal bleeding during the first 2 trimesters. About half of these cases progress to an actual miscarriage. Bleeding and pain accompanying threatened abortion usually are not very intense. Threatened abortion rarely presents with severe vaginal bleeding. On vaginal examination, the cervical os is closed and no cervical motion tenderness or tissue is found. Diffuse uterine tenderness and/or adnexal tenderness may be present. Threatened abortion is defined by the absence of passing/passed tissue and the presence of a closed cervix. These findings differentiate threatened abortion from later stages of abortion.
• Inevitable abortion: Vaginal bleeding is accompanied by dilatation of the cervical canal. Bleeding usually is more severe than with threatened abortion and often is associated with abdominal pain.
• Incomplete abortion: Vaginal bleeding usually is intense and accompanied by abdominal pain. The cervical os is open and products of conception are being passed (confirmed by either patient report or evidence upon examination). Ultrasonography reveals that some products of conception still are present in the uterus.
• Complete abortion: Patients usually present with a history of bleeding, abdominal pain, and tissue passage. By the time miscarriage is complete, bleeding and pain usually have subsided. Diagnosis may be confirmed by observation of the aborted fetus with the complete placenta. Ultrasound reveals a vacant uterus.

Frequency

United States

Approximately 5-15% of diagnosed pregnancies result in spontaneous abortion.

International

Some European investigators quote the rate of spontaneous abortion to be as low as 2-5%.

Clinical

History

• Patients with spontaneous abortion usually present to the ED with vaginal bleeding and/or abdominal pain.
  • Vaginal bleeding may vary from slight spotting to a severe life-threatening hemorrhage. Quantification of the amount of bleeding is very important. The patient's history should reflect the number of pads or tampons used.
  • Presence of blood clots or tissue may be an important sign indicating progression of spontaneous abortion.
  • Abdominal pain usually is located in the suprapubic area or in one or both lower quadrants.
  • Pain may radiate to the lower back, buttocks, genitalia, and perineum.
• Other symptoms, such as fever or chills, are more characteristic of a septic abortion.
• Consider any woman of childbearing age with vaginal bleeding pregnant until proven otherwise.

Physical

Immediately evaluate patients who are experiencing hemodynamic instability or severe vaginal bleeding, including orthostatic vital signs and abdominal and pelvic examinations. Initiate emergency fluid resuscitation in cases of orthostatic hypotension.

• Pelvic examination should focus on determining the source of bleeding.
  • Blood from cervical os
  • Intensity of bleeding
  • Presence of clots or tissue fragments
  • Cervical motion tenderness (presence increases suspicion for ectopic pregnancy)
  • State of cervical os: Open indicates inevitable or incomplete abortion; closed indicates threatened abortion.
  • Uterine size and tenderness, as well as adnexal tenderness or masses

Causes

• Embryonic abnormalities account for 80-90% of first-trimester miscarriages.
  • Chromosomal abnormalities are the most common cause of spontaneous abortion.
  • More than 90% of cytogenic and morphologic errors are eliminated through spontaneous abortion.
  • Chromosomal abnormalities have been found in more than 75% of fetuses aborted in the first trimester.
  • The rate of chromosomal abnormalities increases with age, with a steep increase in women older than 35 years.
• Maternal factors account for the majority of second-trimester abortions. These factors can be divided into 4 categories.
  • Chronic maternal health factors
    • Maternal insulin-dependent diabetes mellitus (IDDM): As many as 30% of pregnancies in women with IDDM result in spontaneous abortion, predominantly in patients with poor glucose control in the first trimester.
    • Severe hypertension
    • Renal disease
    • Systemic lupus erythematosus (SLE)
    • Hypothyroidism and hyperthyroidism
  • Acute maternal health factors
    • Infections (eg, rubella, cytomegalovirus [CMV], and mycoplasmal ureaplasmal, listerial, toxoplasmal infections)
    • Trauma
  • Severe emotional shock
• Diseases and abnormalities of the reproductive system
  • Congenital or acquired uterine defects
  • Fibroids
  • Cervical incompetence
  • Abnormal placental development
  • Grand multiparity
• Exogenous factors
  • Caffeine
  • Alcohol
  • Tobacco
  • Cocaine

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