Spontaneous Abortion

Early spontaneous abortion is often caused by a chromosomal abnormality. Maternal reproductive tract abnormalities (eg, bicornuate uterus, fibroids, adhesions) may also cause pregnancy loss through 20 weeks gestation. Isolated spontaneous abortions may result from certain viral infections—most notably cytomegalovirus, herpesvirus, parvovirus, and rubella virus. Other causes include immunologic abnormalities and major physical trauma. Most often, the cause is unknown.

Risk factors for spontaneous abortion include

• Extremes of maternal age

• History of spontaneous abortion

• Cigarette smoking

• Use of certain substances (eg, , alcohol)

• A poorly controlled chronic disease (eg, diabetes, hypertension, overt thyroid disorders) in the mother

In a national database study, the risks of miscarriage across maternal age groups were as follows: < 20 years (17%); 20 to 24 (11%); 25 to 29 (10%); 30 to 34 (11%); 35 to 39 (17%); 40 to 44 (33%); > 45 (57%) (1).

Subclinical thyroid disorders, a retroverted uterus, and minor trauma have not been shown to cause spontaneous abortions.

Symptoms of spontaneous abortion include crampy pelvic pain, uterine bleeding, and eventually expulsion of tissue.

Bleeding in early pregnancy is common; in one study of over 4500 women, bleeding occurred in approximately 25% of first-trimester pregnancies, and 12% of pregnancies with bleeding resulted in pregnancy loss (1).

Late spontaneous abortion may begin with a gush of fluid when the membranes rupture. Hemorrhage is rarely massive. A dilated cervix indicates that abortion is inevitable.

If products of conception remain in the uterus after spontaneous abortion, uterine bleeding may occur, sometimes after a delay of hours to days. Infection may also develop, causing fever, pain, and sometimes sepsis (called septic abortion).

• Transvaginal ultrasonography

• Pelvic examination

Pregnancy is diagnosed with a urine or serum beta-hCG test. Transvaginal ultrasonography is the main method used to evaluate for spontaneous abortion. If ultrasonography is not available, hCG results may be informative. There is no single hCG level that is diagnostic of spontaneous abortion; serial beta-hCG levels that decrease across several measurements are consistent with a failed pregnancy.

Transvaginal ultrasonography is performed to confirm intrauterine pregnancy and check for fetal cardiac activity, which is usually detectable after 5.5 to 6 weeks gestation. However, gestational age is often somewhat uncertain, and serial ultrasonography is often required. If cardiac activity is absent and had been detected previously during the current pregnancy, fetal demise is diagnosed.

In early pregnancy, for patients with suspected spontaneous abortion, transvaginal ultrasound findings diagnostic of pregnancy failure are one or more of the following (1):

• Crown-rump length ≥ 7 mm and no heartbeat

• Mean sac diameter ≥ 25 mm and no embryo

• Absence of an embryo with a heartbeat, after a previous scan in current pregnancy: ≥ 2 weeks earlier that showed a gestational sac without a yolk sac OR ≥ 11 days earlier in the current pregnancy that showed a gestational sac with a yolk sac

There are many ultrasound findings that raise suspicion for but are not diagnostic of pregnancy failure, including characteristics of the gestational or yolk sac, absence of embryo or heartbeat, and crown-rump length. If these findings are present, serial evaluation is required to confirm whether a pregnancy is viable.

Traditionally, the status of the abortion process is classified as follows:

• Threatened abortion: Patients have uterine bleeding and it is too early to assess whether the fetus is alive and viable and the cervix is closed. Potentially, the pregnancy may continue without complications.

• Inevitable abortion: The cervix is dilated. If the cervix is dilated, the volume of bleeding should be evaluated because it is sometimes significant.

• Incomplete abortion: The products of conception are partially expelled.

• Complete abortion: The products of conception have passed and the cervix is closed (see table Characteristic Symptoms and Signs in Spontaneous Abortions).

• Missed abortion: Death of an embryo or a fetus is confirmed, but there is no bleeding or cervical dilation and the products of conception have not been expelled.

An anembryonic pregnancy (formerly blight ovum) refers to a nonviable pregnancy with a gestational sac, but with no yolk sac or embryo visualized on transvaginal ultrasonography.

For recurrent pregnancy loss, typically testing is done to determine the cause of abortion.

• For threatened abortion, observation

• For inevitable, incomplete, or missed abortions, observation or surgical or medical uterine evacuation

• If the mother is Rh-negative, Rho(D) immune globulin

• Pain medication as needed

• Emotional support

For threatened abortion, treatment is observation, but clinicians may periodically evaluate the woman's symptoms or do ultrasonography to check fetal status. No evidence suggests that bed rest decreases risk of subsequent completed abortion.

For inevitable, incomplete, or missed abortions, treatment is waiting for spontaneous passage of products of conception, management with medications, or uterine evacuation.

In the first trimester, expectant management is an option, but this approach is not recommended during the second trimester due to limited safety studies and risk of hemorrhage (1). Expectant management has an 80% success rate for complete expulsion within 8 weeks, with symptomatic women having better outcomes than asymptomatic women. Bleeding and cramping may occur, and patients should be counseled about when to return to the healthcare facility if symptoms are severe or to confirm passage of gestational tissue. Ultrasound and reported symptoms are used to confirm passage of gestational tissue; in a patient with a previous ultrasound that showed a gestational sac, a follow-up ultrasound with no gestational sac is the most common criterion for complete expulsion. For patients who cannot return for ultrasound confirmation, triaging via telemedicine and/or home urine pregnancy tests may be useful. If complete expulsion is not achieved within a reasonable time, medical management or surgery may be necessary. 

1).

Spontaneous abortions that are not completely expelled with expectant management or medications require surgical uterine evacuation. Also, some women may prefer surgical evacuation due to more immediate completion and less need for follow-up care. Traditionally, uterine evacuation was performed with sharp curettage alone. However, suction curettage is now favored due to superior outcomes and can be completed in an office setting with local anesthesia and/or sedation in first trimester loss patients.

Urgent surgical evacuation may be needed in cases of hemorrhage, hemodynamic instability, or infection.

If complete abortion seem likely based on symptoms and/or ultrasound, further management with medications or uterine evacuation is typically not required. Uterine evacuation may be needed if bleeding occurs and/or if other signs indicate that products of conception may be retained.

Pain medications should be given, as appropriate. Rho(D) immune globulin is given if the pregnant patient is Rh-negative.

After a spontaneous abortion, parents may feel grief or guilt. They should be given emotional support and, in most cases of spontaneous abortions, reassured that their actions were not the cause. Formal counseling or support groups may be made available if appropriate.