OVERVIEW: What every practitioner needs to know

Spontaneous abortion (SAB) may be diagnosed incidentally on ultrasound or may present with amenorrhea, vaginal bleeding, and/or pelvic pain. A pregnancy test should performed on all women of childbearing age who present with vaginal bleeding. Physical exam is important to assess hemodynamic stability, abdominal tenderness or peritoneal signs, the degree of bleeding, uterine size, and cervical dilation.

Pelvic ultrasound is the diagnostic test of choice for spontaneous abortion and may, in combination with physical exam findings, reveal a threatened abortion, complete abortion, incomplete abortion, inevitable abortion, or early pregnancy failure. If the ultrasound is nondiagnostic and the patient did not have a previously documented intrauterine pregnancy, then ectopic pregnancy must be ruled out.

For women who are stable at less than 12 weeks with spontaneous abortion, then management options include expectant, misoprostol, or surgical evacuation of the uterus. Women should be counseled regarding the risks and benefits of each management option and allowed to choose according to their personal preferences.

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Are you sure your patient is experiencing a spontaneous abortion? What are the typical findings for this disease?

The most common symptoms of spontaneous abortion are:

1. Vaginal bleeding

2. Abdominal or pelvic pain

3. Amenorrhea

Other symptoms may include passage of tissue from the vagina, fever or chills, malaise, and the loss of normal pregnancy-related symptoms such as breast tenderness and nausea. Women may also be asymptomatic.


Spontaneous abortion: Pregnancy that ends spontaneously before the fetus has reached a viable gestational age. This is typically defined as an embryo or fetus weighing 500 g or less, or less than 22 to 24 weeks gestational age.

Complete abortion: Passage of all the products of conception. Before 12 weeks of gestation, it is possible for all the uterine contents to be expelled.

Incomplete abortion: Passage of some, but not all, products of conception. After 12 weeks of gestation, it is common for the fetus to pass but placental tissue may be retained.

Threatened abortion: Vaginal bleeding through a closed cervical os in the presence of a viable intrauterine gestation.

Inevitable abortion: Vaginal bleeding through an open cervical os in the presence of a viable intrauterine gestation.

Missed abortion: In-utero death of the embryo or fetus prior to viability. Also known as early pregnancy failure, which can be divided into anembryonic pregnancy (“blighted ovum”) and embryonic / fetal demise. Currently, missed abortion is an ultrasound diagnosis. However, the term originated before the development of ultrasound, when a nonviable pregnancy was retained in the uterus without spontaneous passage for at least 8 weeks since the demise.

Septic abortion: A rare complication of spontaneous abortion, more common with retained products of conception, where intrauterine infection may spread, causing sepsis.

Recurrent pregnancy loss: Classically defined as 3 or more consecutive spontaneous abortions. Some experts advocate that 2 or more consecutive spontaneous abortions should prompt an evaluation, especially in women over age 35.

What other disease/condition shares some of these symptoms?

Gynecologic- Pregnancy-related, so may also have amenorrhea and/or vaginal bleeding and pain

Normal pregnancy

Ectopic pregnancy

Molar pregnancy

Post-abortion endometritis

Gynecologic- Non-pregnancy-related

Cervicitis / Pelvic inflammatory disease

Tubo-ovarian abscess

Ovarian torsion

Ovarian cyst rupture

Hemorrhagic or ruptured corpus luteum

Cervical polyps, malignancy, excessive friability


Acute appendicitis

Renal stone

What caused this disease to develop at this time?

Commonly cited risk factors (in order of highest strength of association) for spontaneous abortion may include:

  • Increasing maternal age

  • First trimester bleeding

  • History of previous spontaneous abortion

  • Moderate alcohol consumption

  • Smoking

  • Cocaine

  • NSAIDs

Causes of spontaneous abortion may include:

  • Unexplained

  • Chromosomal abnormalities

    Autosomal trisomies are the most common (trisomy 16 is found most frequently), followed by monosomy X and polyploidies.

  • Congenital anomalies

  • Endocrine abnormalities, including thyroid disease

  • Reproductive tract abnormalities, including submucosal fibroids and uterine anomalies

  • Infection

  • Systemic maternal diseases such as diabetes mellitus, lupus, chronic renal failure, antiphospholipid antibody syndrome

  • Environmental causes such as radiation, smoking, alcohol, anesthetic gases

  • Intrauterine procedures such as chorionic villus sampling and amniocentesis

  • Blunt abdominal trauma in the second trimester


Women actively in the process of having a spontaneous abortion will report amenorrhea, vaginal bleeding, and/or pelvic pain. Women may also be diagnosed with a failed pregnancy incidentally on ultrasound, so may be asymptomatic.


Physical exam should include vital signs, and abdominal and pelvic exam. Depending on the amount of blood loss, the patient may be hemodynamically unstable. An abdominal exam should evaluate for tenderness and any peritoneal signs, such as rebound or guarding, that may indicate an ectopic pregnancy. A speculum exam should be performed to assess how briskly the patient is bleeding from the uterus and identify any other sources of bleeding. A bimanual pelvic exam will allow for assessment of uterine size and cervical dilation as well as adnexal mass or tenderness.

Threatened abortion is defined as bleeding through a closed os. The bleeding may be painless or accompanied by mild pelvic pain. The pregnancy on ultrasound will be viable.

Inevitable abortion is defined as bleeding through an open os. The bleeding is usually accompanied by pain. There may be products of conception visualized at the os. As seen on ultrasound, however, the pregnancy will still be present in the uterus and viable.

Incomplete abortion is defined as the passage of some, but not all, products of conception. Typically, the cervical os will be open and the uterus is not well contracted. The bleeding can be extremely heavy and cause hemodynamic instability.

Complete abortion is defined as the passage of all the products of conception. The uterus should be small and well contracted with a closed cervix . Bleeding should be minimal.

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

  • CBC (to assess degree of bleeding)

  • Type & screen (T&S) (Rhogam for Rh (D) negative women)

  • Quantitative beta-human chorionic gonadotropin (β-hCG) (if ultrasonography is nondiagnostic).

Would imaging studies be helpful? If so, which ones?

Pelvic ultrasound is the imaging study of choice for the evaluation of spontaneous abortion. The ultrasound results will aid in distinguishing between a viable and non-viable intrauterine pregnancy and an intrauterine compared with extrauterine pregnancy.

Intrauterine pregnancy with yolk sac or embryo on ultrasound effectively rules out ectopic pregnancy, with the rare exception of heterotopic pregnancy (1/4000). With transvaginal ultrasound (TV-US), using generous cutoffs, a yolk sac should be visualized when the mean gestational sac diameter is 10 mm. An embryo should be visualized when the mean gestational sac diameter is 20 mm. Cardiac activity should be visualized when the crown-rump length of the embryo is more than 5 mm. If these criteria are not met, an early pregnancy failure can be diagnosed.

If the pregnancy is highly desired and the results are borderline, then the ultrasound can be repeated in one week to check for appropriate growth.

There is typically no role for β-hCG monitoring once the presence of an intrauterine pregnancy has been established by ultrasound.

Other ultrasound signs predictive for potential pregnancy loss include abnormal yolk sac (large, irregular, free-floating) , irregular gestational sac, and slow fetal heart rate (< 100 bpm at 5 to 7 weeks gestation).

Whether or not a subchorionic hematoma is predictive of poor fetal outcome is controversial.

For women with a previously known intrauterine pregnancy, an ultrasound showing an empty uterus likely indicates a complete spontaneous abortion, taking into account history and exam findings. The ultrasound may also show evidence of retained products of conception. The ultrasound diagnosis of retained products of conception is not always accurate, however. Therefore, ultrasound findings must be correlated with the patient’s symptoms. No endometrial thickness measurement has been shown to reliably predict the need for intervention.

For women who have not yet had a documented intrauterine pregnancy, an empty uterus on ultrasound with a positive pregnancy test is suspicious for ectopic pregnancy. These women should be ruled out for ectopic pregnancy with serial b-hCG levels (see laboratory studies above). The rate of b-hCG decline in a spontaneous abortion should be at least 21%-35% in 2 days and at least 60%-84% in 7 days.

Confirming the diagnosis

Please see Figure 1. Algorithm for Early Spontaneous Abortion Management (<12 weeks)

Figure 1.

Algorithm for Early Spontaneous Abortion Management (<12 weeks)

Management of threatened abortion

Vaginal bleeding can occur in normal pregnancies. There is no proven treatment for threatened abortion besides expectant management. While abstinence from sexual activity may be recommended, there is no evidence that this impacts the clinical outcome. Similarly, bedrest has not been shown to be helpful in the setting of threatened abortion. If there is a viable pregnancy on ultrasound, the rate of ongoing pregnancy is approximately 85%. Rh(D) immune globulin (Rhogam) should be given to Rh (D) negative mothers.

If you are able to confirm that the patient is having a spontaneous abortion, what treatment should be initiated?

If the patient is hemodynamically unstable with vaginal bleeding and/or sepsis, priorities include:

  • Support hemodynamically with oxygen, cardiac monitor, NPO, IV access, IV fluids, type and cross for possible transfusion, endometrial and blood cultures and antibiotics as indicated

  • Consult obstetrics-gynecology for urgent evaluation

For women with septic abortions, or suspicion of intrauterine infection along with incomplete, inevitable, or missed abortion, then the treatment of choice is IV broad spectrum antibiotics and surgical evacuation of the uterus. It is important that a loading dose of antibiotics is given prior to surgical evacuation. For women with a complete abortion and mild postabortal endometritis, then outpatient treatment with oral antibiotics is appropriate.

For women with pregnancies > 12 weeks in size and a fetal demise, incomplete abortion, or inevitable abortion has been diagnosed, management options include surgical evacuation of the uterus or induction of labor in the inpatient setting. The need for emergent treatment would be based on the patient’s signs and symptoms. Expectant management would not be advised.

If the patient is hemodynamically stable with known incomplete, inevitable, or missed abortion less than 12 weeks in size and without infection, there are 3 potential management pathways: expectant, medical, and surgical. (See Table I. Treatment Options for Spontaneous Abortion.)

Expectant management: This strategy allows the spontaneous passage of the products of conception. It may take 4 to 6 weeks for passage to occur and the timing is unpredictable. The efficacy is higher with incomplete abortion (91%) compared with embryonic or fetal demise (76%) and anembryonic pregnancy (66%). These success rates reflect waiting up to 4 weeks for passage of the pregnancy. Success rates will be lower if only 1 to 2 weeks are allowed. Some women prefer this option because it is perceived as more natural and the risks of surgery and anesthesia are avoided. Women can change their minds and switch to medical or surgical management at any time. Follow-up should include documentation of complete abortion.

Contraindications to expectant management:

  • Suspected ectopic or molar pregnancy

  • •Diagnosis of SAB not yet confirmed (and the pregnancy is desired)

  • •Symptoms of pelvic infection or sepsis

  • •Hemodynamic instability or shock

  • •Uterine contents/volume > 12 wk size

  • •Bleeding disorder, anti-coagulated

  • •IUD in place (remove it first)

  • •Severe anemia

Medical management: This option utilizes misoprostol, a prostaglandin E1 analog, to induce expulsion of the products of conception from the uterus. Misoprostol causes cervical ripening and uterine contractions. Women should expect pain and bleeding as the products of conception are passed. Women can be given NSAIDs and a narcotic for painful cramping.

The most commonly accepted regimen is 800 mcg of misoprostol vaginally (with a repeat dose as needed). In one large trial, this regimen was found to be 71% effective with one dose, which increased to 84% after 2 doses. Success rates were 93% for incomplete or inevitable abortion, 88% for embryonic or fetal demise, and 81% for anembryonic gestation. Side effects of misoprostol include nausea, vomiting, fever, chills, and diarrhea.

Women should expect a longer duration of bleeding with medical management compared to surgical management, on average 2 weeks, but this bleeding rarely requires surgical intervention. Protocols for misoprostol treatment include follow-up to document complete abortion with either repeat ultrasound documenting absence of the gestational sac or serial b-hCG levels (decrease in b-hCG of 80% at one week following passage of tissue).

Alternative regimens for incomplete abortion include 600 mcg of misoprostol orally or 400 mcg of misoprostol sublingually.

Contraindications to medical management with misoprostol:

  • •Suspected ectopic or molar pregnancy

  • Diagnosis of SAB not yet confirmed (and the pregnancy is desired)

  • •Symptoms of pelvic infection or sepsis

  • Hemodynamic instability or shock

  • Uterine contents/volume > 12 wk size

  • Bleeding disorder, anti-coagulated

  • IUD in place (remove it first)

  • Allergy to misoprostol

  • Severe anemia

Surgical management: Surgical management involves performing a suction dilation and curettage (D&C) procedure, either in the office or the operating room depending on the woman’s preference, medical history, and degree of anesthesia required. The suction can be performed with either a manual vacuum aspirator or an electric suction device. Surgical management has the highest success rate for complete abortion, approximately 98%. Surgical management also offers the fastest resolution for SAB, with less bleeding than expectant or medical management.

Contraindications to surgical management:

  • •Diagnosis of SAB not yet confirmed (and the pregnancy is desired)

  • Uncorrected coagulopathy

As all three options are safe and reasonable, if the patient is a candidate for expectant or medical management, then her preferences after counseling should decide the course of treatment. Studies have shown that all three options are acceptable to women.

What are the adverse effects associated with each treatment option?

Expectant management: Unpredictable timing, pain, and bleeding associated with passage of the products of conception; potential need for emergent surgical evacuation

Medical management: Side effects of misoprostol; pain and bleeding associated with passage of the products of conception; potential need for emergent surgical evacuation

Surgical management: Risks of suction D&C including bleeding, infection, retained POCs, injury to the cervix, uterus, or other internal organs, intrauterine synechiae (Asherman’s syndrome), and the risks of anesthesia

Post abortion care

Rh(D) immune globulin (Rhogam) should be given to Rh (D) negative mothers. Grief counseling should be offered as appropriate. Menses should return 4 to 6 weeks after the passage of products of conception or surgical evacuation of the uterus. Contraception, if desired, can be started immediately after complete abortion is documented. Most providers counsel women to have nothing per vagina, including sexual activity and tampons, for at least 2 weeks. Women can attempt to conceive again as soon as they feel emotionally and physically ready.

What are the possible outcomes of spontaneous abortion?

The risk of repeat SAB is 20% after one miscarriage (same as baseline risk), 28% after two consecutive miscarriages, and 43% after 3 or more consecutive miscarriages. If there is a known etiology of the miscarriage, couples can be counseled on recurrence risks. If the etiology is unknown, women should be reassured that nothing they did or did not do caused the miscarriage. Including the partner in this discussion can be helpful. Addressing reversible risk factors in a non-judgmental way may be appropriate.

What causes this disease and how frequent is it?

Spontaneous abortion is very common, occurring in up to 20% of all pregnancies. Eighty percent of these losses occur in the first trimester. Once a fetal heart is documented, the risk of SAB drops to about 5%-10%, depending on maternal age. Approximately 1 in 4 women will experience a miscarriage in her lifetime.

The most important risk factors for SAB are increasing maternal age and previous SAB. Other risk factors include heavy smoking, moderate to high alcohol consumption, cocaine, and possibly NSAIDs. Being extremely underweight or overweight has also been associated with SAB.

Approximately 40%-50% of spontaneous abortions are caused by chromosomal abnormalities including autosomal trisomies, monosomy X, and polyploidies. Most of these abnormalities arise in the embryo spontaneously. The earlier the pregnancy loss, the more likely it is due to a chromosomal abnormality. Rarely, the chromosomal abnormality may result from a parental karyotype abnormality such as a balanced translocation.

Congenital anomalies and trauma, including invasive procedures such as CVS and amniocentesis, can also cause SAB.

Maternal factors such as systemic illnesses, infection, endocrinopathies, antiphospholipid antibody syndrome, submucosal uterine fibroids, and uterine anomalies can also cause SAB.

Finally, some spontaneous abortions are unexplained.

How do these pathogens/genes/exposures cause the disease?

Other clinical manifestations that might help with diagnosis and management

What complications might you expect from the disease or treatment of the disease?

Are additional laboratory studies available; even some that are not widely available?


Progesterone generally remains constant during the first trimester and is not specific to gestational age like b-hCG values. However, it can be an adjunct in evaluating normal and abnormal pregnancy. Levels less than 5 ng/ml are 100% specific for abnormal pregnancy—either nonviable intrauterine pregnancy or ectopic pregnancy. Values greater than 20-25 ng/ml have a 100% positive predictive value for normal pregnancy. Many values remain in the indeterminate range (5-20 ng/ml) and are not particularly useful in determining a clear diagnosis.

Progesterone levels are not generally used to evaluate spontaneous abortion, however, as ultrasound provides more useful information.

How can spontaneous abortion be prevented?

Although most SABs are caused by random chromosomal abnormalities that arise in the embryo and are therefore unpreventable, preconception health should be optimized in order to reduce the chances of a future SAB. This may include avoiding tobacco, moderate to heavy alcohol use, cocaine, and NSAIDs when trying to conceive. Women should aim to achieve a healthy body weight prior to conception and should be consuming a daily multivitamin with folic acid (400 to 800 mcg) daily.

If a woman is taking a teratogenic medication, she should be transitioned to an alternative prior to conception.

Finally, women with medical problems such as diabetes mellitus, hypertension, lupus, and thyroid disease should have their disease under control prior to conception.

What is the evidence?

Morin, L, Van den Hof, MC. “Diagnostic Imaging Committee, Society of Obstetricians and Gynaecologists of Canada. Ultrasound evaluation of first trimester pregnancy complications”. J Obstet Gynaecol Can. vol. 27. 2005. pp. 581-91. •Society of Obstetricians and Gynaecologists of Canada's Clinical Practice Guidelines, providing ultrasound definitions of early pregnancy failure and ectopic pregnancy.

Neilson, JP, Hickey, M, Vazquez, JC. “Medical treatment for early fetal death (less than 24 weeks)”. Cochrane Database Syst Rev. 2006. pp. CD002253•Review of trials of misoprostol for the medical management of missed abortion establishes vaginal misoprostol as the treatment of choice.

Luise, C, Jermy, K, May, C. “Outcome of expectant management of spontaneous first trimester miscarriage: observational study”. BMJ. vol. 324. 2002. pp. 873-5. •Describes rates of complete abortion with expectant management.

Chen, BA, Creinin, MD. “Contemporary management of early pregnancy failure”. Clinical Obstet Gynecol. vol. 50. 2007. pp. 67-88. •Thorough review of modern definitions of early pregnancy failure and management options including expectant, medical, and surgical.

Barnhart, K, Sammel, MD, Chung, K. “Decline of serum human chorionic gonadotropin and spontaneous complete abortion: defining the normal curve”. Obstet Gynecol. vol. 104. 2004. pp. 975-81. •Establishes the normal rate of decline of b-hCG levels in spontaneous abortion.

Nanda, K, Peloggia, A, Grimes, DA. “Expectant care versus surgical treatment for miscarriage”. Cochrane Database Syst Rev. 2006. pp. CD003518•Review of trials comparing expectant management and surgery for spontaneous abortion establishes both as viable options.

Zhang, J, Gilles, JM, Barnhart, K. “A comparison of medical management with misoprostol and surgical management for early pregnancy failure”. N Engl J Med. vol. 353. 2005. pp. 761-9. •Seminal trial evaluating the efficacy, safety, and acceptability of misoprostol for miscarriage compared to surgical management.

Regan, L, Braude, PR, Trembath, PL. “Influence of past reproductive performance on risk of spontaneous abortion”. BMJ. vol. 299. 1989. pp. 541-5. •Provides estimates of risk of repeat spontaneous abortion.

Neilson, JP, Gyte, GML, Hickey, M. “Medical treatments for incomplete miscarriage (less than 24 weeks)”. Cochrane Database Syst Rev. 2010. pp. CD007223•Cochrane review on expectant management compared to surgery and misoprostol compared to surgery for incomplete abortion.

Stubblefield, PG, Grimes, DA. “Septic Abortion”. N Eng J Med. vol. 331. 1994. pp. 310-4. •Review article outlining management of septic abortion.

Griebel, CP, Halvorsen, J, Golemon, TB, Day, AA. “Management of spontaneous abortion”. Am Fam Physician. vol. 72. 2005. pp. 1243-50. •Review article on the diagnosis and management of spontaneous abortion.

Schauberger, C, Mathiason, M, Rooney, B. “Ultrasound assessment of first trimester bleeding”. Obstet Gynecol. vol. 105. 2005. pp. 333-8. •Reports outcomes of threatened abortion.