Spontaneous Abortion


Essentials of Diagnosis

  • Intrauterine pregnancy at less than 20 weeks.
  • Low or falling levels of hCG.
  • Bleeding, midline cramping pain.
  • Open cervical os.
  • Complete or partial expulsion of products of conception.

General Considerations

About three-fourths of spontaneous abortions occur before the 16th week; of these, three-fourths occur before the eighth week. Almost 20% of all clinically recognized pregnancies terminate in spontaneous abortion.

More than 60% of spontaneous abortions result from chromosomal defects due to maternal or paternal factors; about 15% appear to be associated with maternal trauma, infections, dietary deficiencies, diabetes mellitus, hypothyroidism, or anatomic malformations. There is no reliable evidence that abortion may be induced by psychic stimuli such as severe fright, grief, anger, or anxiety. In about one-fourth of cases, the cause of abortion cannot be determined. There is no evidence that video display terminals or associated electromagnetic fields are related to an increased risk of spontaneous abortion.

It is important to distinguish women with a history of incompetent cervix from those with more typical early abortion and those with premature labor or rupture of the membranes. Characteristically, incompetent cervix presents as “silent” cervical dilation (ie, with minimal uterine contractions) between 16 and 28 weeks of gestation. Women with incompetent cervix often present with significant cervical dilation (2 cm or more) and minimal symptoms. When the cervix reaches 4 cm or more, active uterine contractions or rupture of the membranes may occur secondary to the degree of cervical dilation. This does not change the primary diagnosis. Factors that predispose to incompetent cervix are a history of incompetent cervix with a previous pregnancy, cervical conization or surgery, cervical injury, DES exposure, and anatomic abnormalities of the cervix. Prior to pregnancy or during the first trimester, there are no methods for determining whether the cervix will eventually be incompetent. After 14-16 weeks, ultrasound may be used to evaluate the internal anatomy of the lower uterine segment and cervix for the funneling and shortening abnormalities consistent with cervical incompetence.

Clinical Findings

A. Symptoms and Signs
1. Threatened abortion
Bleeding or cramping occurs, but the pregnancy continues. The cervix is not dilated.

2. Inevitable abortion
The cervix is dilated and the membranes may be ruptured, but passage of the products of conception has not occurred. Bleeding and cramping persist, and passage of the products of conception is considered inevitable.

3. Complete abortion
The fetus and placenta are completely expelled. Pain ceases, but spotting may persist.

4. Incomplete abortion
Some portion of the products of conception (usually placental) remain in the uterus. Only mild cramps are reported, but bleeding is persistent and often excessive.

5. Missed abortion
The pregnancy has ceased to develop, but the conceptus has not been expelled. Symptoms of pregnancy disappear. There is a brownish vaginal discharge but no free bleeding. Pain does not develop. The cervix is semifirm and slightly patulous; the uterus becomes smaller and irregularly softened; the adnexa are normal.

B. Laboratory Findings
Pregnancy tests show low or falling levels of hCG. A complete blood count should be obtained if bleeding is heavy. Determine Rh type, and give Rho(D) immune globulin if the type is Rh-negative. All tissue recovered should be assessed by a pathologist and may be sent for genetic analysis in selected cases.

C. Ultrasonographic Findings
The gestational sac can be identified at 5-6 weeks from the LMP, a fetal pole at 6 weeks, and fetal cardiac activity at 6-7 weeks. Serial observations are often required to evaluate changes in size of the embryo. A small, irregular sac without a fetal pole with accurate dating is diagnostic of an abnormal pregnancy.

Differential Diagnosis

The bleeding that occurs in abortion of a uterine pregnancy must be differentiated from the abnormal bleeding of an ectopic pregnancy and anovular bleeding in a nonpregnant woman. The passage of hydropic villi in the bloody discharge is diagnostic of hydatidiform mole.


A. General Measures
1. Threatened abortion
Place the patient at bed rest for 24-48 hours followed by gradual resumption of usual activities, with abstinence from coitus and douching. Hormonal treatment is contraindicated. Antibiotics should be used only if there are signs of infection.

2. Missed or inevitable abortion
This calls for counseling regarding the fate of the pregnancy and planning for its elective termination at a time chosen by the patient and physician. Insertion of a laminaria to dilate the cervix followed by aspiration is the method of choice for a missed abortion. Prostaglandin vaginal suppositories are an effective alternative.

B. Surgical Measures
1. Incomplete abortion
Prompt removal of any products of conception remaining within the uterus is required to stop bleeding and prevent infection. Analgesia and a paracervical block are useful, followed by uterine exploration with ovum forceps or uterine aspiration.

2. Cerclage and restriction of activities
These are the treatment of choice for incompetent cervix. A variety of suture materials including a 5-mm Mersilene band can be used to create a purse-string type of stitch around the cervix, using either the McDonald or Shirodkar method. Cerclage should be undertaken with caution when there is advanced cervical dilation or when the membranes are prolapsed into the vagina. Rupture of the membranes and infection are specific contraindications to cerclage. Cervical cultures for N gonorrhoeae, chlamydia, and group B streptococci should be obtained before or at the time of cerclage.

George L et al: Plasma folate levels and risk of spontaneous abortion. JAMA 2002;288:1867.

Provided by ArmMed Media
Revision date: June 20, 2011
Last revised: by Jorge P. Ribeiro, MD