eMedicine Specialties > Emergency Medicine > Obstetrics & Gynecology

Abortion, Complete

Author: Verena T Valley, MD, Associate Professor, Director of Ultrasound, Department of Emergency Medicine, University of Mississippi School of Medicine
Coauthor(s): Loretta Jackson-Williams, MD, PhD, Assistant Professor, Department of Emergency Medicine, University of Mississippi Medical Center; Christopher A Fly, MD, Assistant Professor, Department of Emergency Medicine, Medical College of Georgia
Contributor Information and Disclosures

Updated: May 30, 2006

Introduction

Background

The most common complication of pregnancy is spontaneous abortion, which is estimated to occur in 10-15% of pregnancies. Spontaneous abortion can be classified as threatened, inevitable, incomplete, complete, or missed. Spontaneous abortions can further be categorized as sporadic or recurrent (>3 occurrences). By definition, a complete abortion is the expulsion of all products of conception before the 20th week of gestation.

Pathophysiology

Pathophysiology of a spontaneous abortion may be suggested by the timing of miscarriage. Chromosomal defects commonly are seen in spontaneous abortions, especially those that occur during 4-8 weeks' gestation. Genetic etiologies are common in early first-trimester loss but may be seen throughout gestation. Trisomy chromosomes are the most common chromosomal anomaly. Insufficient or excessive hormonal levels usually result in spontaneous abortion before 10 weeks' gestation. Infectious, immunologic, and environmental factors generally are seen in first-trimester pregnancy loss. Anatomic factors usually are associated with second-trimester loss. Factor XIII deficiency and a complete or partial deficiency of fibrinogen are associated with recurrent spontaneous abortions.

Frequency

United States

Many pregnancies are not viable. An estimated 50% of pregnancies are terminated spontaneously before the first missed menstrual period and, therefore, usually are not clinically recognized. Spontaneous abortion typically is defined as a clinically recognized (eg, by blood test, ultrasound) pregnancy loss before 20 weeks' gestation. This loss occurs in an estimated 10-20% of pregnancies.

Mortality/Morbidity

Surveillance data from the US between 1987 and 1990 revealed a total of 1459 pregnancy-related deaths. Spontaneous and induced abortions accounted for 5.6% of these deaths.

Race

Surveillance data for pregnancy-related deaths between 1987 and 1990 demonstrated that more black mothers died after ectopic pregnancies and abortions, both spontaneous (14%) and induced (7%), than white mothers (8% and 4%, respectively).

Age

• Age and increased parity affect a woman's risk of a miscarriage. In women younger than 20 years, miscarriage occurs in an estimated 12% of pregnancies; in women older than 20 years, miscarriage occurs in an estimated 26% of pregnancies.
• Age primarily affects the oocyte. When oocytes from young women are used to create embryos for transfer to older recipients, implantation and pregnancy rates mimic those seen in younger women. The number of miscarriages and chromosomal anomalies decreases, suggesting that the uterus is not responsible for poor outcomes in women of advanced reproductive age.

Clinical

History

• Date of last menstrual period
• Estimated length of gestation
• Bleeding
  • Degree - Important to establish whether the patient has been spotting or bleeding in a fashion similar to a heavy menstrual period
  • Duration
  • Presence or passage of tissue
• Bleeding disorders

Physical

• On pelvic examination, the cervix should be closed, and the uterus should be contracted.
• If adnexal tenderness is present, suspect the presence of an ectopic pregnancy.

Causes

Proposed etiologies for spontaneous abortions include the following:

• Genetic factors
  • Approximately 5% of spontaneous abortions occur because of genetic factors.
  • Trisomy chromosomes commonly are encountered. Trisomy 16 accounts for approximately a third of chromosomal abnormalities in early pregnancy.
• Anatomic factors: Congenital or acquired anatomic factors reportedly are present in 10-15% of women who have recurrent spontaneous abortions.
  • Congenital anatomic lesions include müllerian duct anomalies (eg, septate uterus, diethylstilbestrol [DES]-related anomalies). Müllerian duct lesions usually are found in second-trimester pregnancy loss. Anomalies of the uterine artery with compromised endometrial blood flow are congenital.
  • Acquired lesions are intrauterine adhesions (ie, synechiae), leiomyomas, and possibly, adhesions due to endometriosis.
• Endocrine factors
  • Endocrine factors potentially contribute to recurrent abortion in 10-20% of cases.
  • The most common abnormality contributing to spontaneous abortion is luteal phase insufficiency, which occurs when abnormal corpus luteum function results in insufficient progesterone production.
  • Hypothyroidism, hypoprolactinemia, poor diabetic control, and polycystic ovarian syndrome contribute to pregnancy loss.
• Infectious factors
  • Presumed infectious etiology may be found in 5% of cases.
  • Bacterial, viral, parasitic, fungal, and zoonotic infections are associated with recurrent spontaneous abortion.
• Immunologic factors
  • Immunologic factors may contribute in up to 60% of recurrent spontaneous abortions.
  • Both the developing embryo and the trophoblast may be considered immunologically foreign to the maternal immune system. Antiphospholipid antibody syndrome generally is responsible for more second-trimester pregnancy losses than for first-trimester losses.
• Miscellaneous factors
  • Miscellaneous factors may account for as many as 3% of recurrent spontaneous abortions.
  • Other contributing factors implicated in sporadic and recurrent spontaneous abortions include environment, drugs, placental abnormalities, medical illnesses, and male-related causes.

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