Incomplete Miscarriage

Etiology

A specific cause for incomplete expulsion of POC is unclear; however, it may potentially occur following any spontaneous miscarriage or induced abortion.[5][7] Historically, all miscarriages were considered incomplete until uterine curettage confirmed complete expulsion of POC.[5]

Various potential etiologies may result in spontaneous asymptomatic, incomplete, or complete miscarriage. Early pregnancy loss is due to embryonic chromosomal abnormalities in about 50% of cases.[9] Other risk factors include maternal age, maternal comorbidities, especially diabetes, hypertension, renal disease, thyroid disorders, celiac disease, systemic lupus erythematosus (SLE), antiphospholipid syndrome, extremes of weight, structural uterine abnormalities, teratogen exposure (eg, drugs, alcohol, or radiation), some infections (eg, parvovirus B19, syphilis, or Listeria monocytogenes), and trauma.[10][11][12][13] Congenital anomalies and genetic syndromes can also result in miscarriage. 

It is also possible for an induced abortion to result in incomplete passage of POC, similar to a spontaneous incomplete miscarriage.[5] Unsafe abortion may increase the risk of incomplete abortion.[14] Unsafe abortion is defined by the World Health Organization (WHO) as an abortion performed by people lacking the necessary skills or in an environment lacking the minimum medical standards, or both; other definitions also include the use of hazardous techniques, such as ingesting toxic substances, abdominal trauma, and intrauterine instrumentation.[15][16]

Epidemiology

By definition, incomplete pregnancy loss occurs in women with a gestational age of <20 weeks. When all subtypes of miscarriage are considered together, miscarriage occurs in an estimated 10% to 15% of clinically recognized pregnancies; the specific incidence of incomplete miscarriage has not been well documented.[5] In one study, 34% of anembryonic gestations had incomplete expulsion of POC after 1 month, and 26% of pregnancies with embryonic demise managed expectantly did not have complete expulsion of POC after 1 month.[2]

History and Physical

Clinical History

A thorough history should be obtained that includes medical conditions and obstetric and gynecologic history (eg, previous miscarriages, known uterine anomalies, and the first day of the last menstrual period [LMP]) to identify risk factors and patient-specific issues that may affect management.[7] Clinicians should review any previous ultrasounds from the current gestation and compare them with the calculated estimated due date (EDD) from a sure LMP to determine an accurate estimated gestational age, which can influence the preferred treatment modality.[2]

Additionally, clinicians should inquire about presenting symptoms such as cramping and pelvic pain and the quality and quantity of vaginal bleeding noted, including onset, number of saturated pads or tampons per hour, and the number and size of clots present.[2] Clinical features characteristic of incomplete pregnancy loss include the passage of clots or tissue, though it is certainly possible for patients to either be unaware of tissue expulsion that has occurred or mistake blood clot for tissue. Bleeding with an incomplete miscarriage is often prolonged and heavier than typical menses; heavy bleeding is frequently defined as soaking 1 to 2 menstrual pads per hour for 2 hours.[4] Reports of minimal bleeding and identified tissue following a medical or surgical abortion may also indicate an incomplete abortion.[7] Similarly, pain or discomfort should be characterized as this often varies with each individual. With an incomplete pregnancy loss, the pain is often described as severe menstrual cramping that is not resolving.[2] Patient anxiety can also increase the amount of pain experienced.[2]

Physical Examination 

An initial assessment of the patient's hemodynamic stability should include vital signs and a focused physical examination. Findings of hypovolemia (eg, tachycardia and hypotension) are suggestive of hemorrhage secondary to heavy uterine bleeding.[2] A fever is concerning for infection and possible septic miscarriage, which requires emergent obstetrical consultation and surgical intervention.[7][17]

On pelvic examination, typical findings of an incomplete pregnancy loss include an open cervical os with POC visible within the vaginal vault or protruding from the cervix.[2] The presence of purulent vaginal discharge and uterine tenderness strongly suggests infection. The vagina and vulva should also be carefully examined to rule out any nonobstetric causes of bleeding, such as vaginal trauma or bleeding polyps.[7][2][7]

The abdominal exam is typically benign; however, if peritoneal signs are present (eg, rebound tenderness, guarding, and rigidity), obstetrical or general surgery specialists should be consulted, and further evaluation should be emergently performed.[2]

Evaluation

Diagnostic Imaging 

Early pregnancy is best visualized using transvaginal ultrasound; therefore, this modality is preferred when evaluating a suspected pregnancy loss.[18] 

An incomplete pregnancy loss can be confirmed by a transvaginal ultrasound demonstrating the partial expulsion of POC and heterogeneous or echogenic contents within the endometrial cavity or endocervical canal in patients with an open cervical os, particularly if an intrauterine pregnancy was previously diagnosed by ultrasound imaging.[19][18][2] Additional findings on transvaginal ultrasound consistent with retained POC include a mass or focal thickening within the endometrium; occasionally, blood flow can be visualized within this area using Doppler imaging.[18] A nonviable pregnancy noted on imaging with persistent β-human chorionic gonadotropin (β-hCG) levels also suggests an incomplete pregnancy loss.[18]

If no previous imaging studies have established a viable intrauterine pregnancy for comparison, a nonviable pregnancy can be diagnosed with 100% specificity with a single transvaginal ultrasound demonstrating an intrauterine fetal crown-to-rump length of >7 mm without fetal heart tones or if no embryo is noted within a gestational sac with an average diameter of >25 mm.[17]  There is no consensus on transvaginal ultrasound findings indicative of a completed miscarriage; however, the absence of a gestational sac and an endometrial thickness of <30 mm is often used in studies.[4]

Diagnostic Laboratory Studies

The following laboratory studies should be performed to assist in patient management decisions.

β-hCG: The diagnosis of incomplete pregnancy loss is primarily based on clinical assessment and pelvic ultrasound; however, quantitative serum β-human chorionic gonadotropin (β-hCG) levels may be helpful in the diagnostic evaluation of patients without an accurate gestational age due to an unsure LMP or that are found to have a pregnancy of unknown location.[2][20] 

An intrauterine pregnancy typically can be expected to be visible on ultrasound at around 5 to 6 weeks of gestation. However, if the gestational age of a pregnancy is uncertain, a β-hCG level can help a clinician interpret pelvic ultrasound findings.[20] Traditionally, a β-hCG level of 1,000 to 2,000 mIU/mL was used as the "discriminatory zone" at which an intrauterine pregnancy could be visualized by transvaginal ultrasound; if not seen, either ectopic pregnancy or early pregnancy loss was likely. Recently, some studies have recommended that a β-hCG level of >3,500 mIU/mL would be more appropriate as normal intrauterine pregnancies are still possible below that level.[20]

A pregnancy of unknown location refers to a pregnant patient in whom a pelvic ultrasound study does not definitively demonstrate an intrauterine or ectopic pregnancy. In stable patients, β-hCG levels, which increase at a predictable rate in early pregnancy until plateauing at around 10 weeks of gestation, should be followed over several days to observe the trend. A slow increase or decrease in the β-hCG level before its plateau can indicate a failing or abnormal pregnancy.[21][20] It should be noted that ectopic pregnancies may have β-hCG levels that decrease before increasing again, and they can rupture even while β-hCG levels are decreasing. 

A β-hCG level is not diagnostic in itself and should always be interpreted with caution within the larger clinical context to avoid misdiagnosis; whenever the diagnosis of a hemodynamically stable patient is unclear, repeating ultrasound imaging and serial β-hCG levels, typically every 48 hours, are indicated.[18][20]

Hemoglobin and hematocrit: Due to the heavy amount of bleeding typical in most symptomatic patients, assessment for acute blood loss anemia should be performed at the initial presentation.[2]

Blood type with Rh(D) status: A possible transfusion may need to be performed, or Rh(D)-immune globulin administered in Rh(D)-negative patients; therefore, blood typing and Rh(D) status should be obtained with initial laboratory studies.[2]

Pathology studies: Any pregnancy tissue removed from the vagina vault or expelled should be sent for histological examination to confirm pregnancy loss and assess for a molar pregnancy.[17]

Sepsis laboratory studies: For patients where a septic incomplete miscarriage or abortion is suspected, additional laboratory evaluation is indicated, including complete blood count with a differential, comprehensive metabolic panel, serum lactate, blood and urine cultures, and endocervical cultures.[22]

Treatment / Management

Approach to Management 

Early pregnancy loss can generally be managed with expectant, medical, or surgical approaches.[5] Although clinicians traditionally used surgical management in most patients with incomplete pregnancy loss, current US guidelines from the American College of Obstetricians and Gynecologists (ACOG) state that patients with early pregnancy loss can be offered all three approaches (ie, expectant, medical, and surgical) as first-line options and that patient preference should guide management.[4] On the other hand, some guidelines, including those from the National Institutes of Health and Care Excellence (NICE) in the UK, more explicitly prefer 1 to 2 weeks of expectant management as the first-line approach in patients without contraindications. However, NICE guidelines note that medical management should be offered if the patient declines expectant management.[23] In patients with incomplete pregnancy loss, limited evidence suggests that medical management may not be any more beneficial than expectant management. Depending on clinical and patient factors, any of these approaches can be appropriate.[5] (A1)

Expectant and Medical Management

Expectant management consists of the watchful monitoring of patients without contraindications to this approach, allowing the natural process of miscarriage to progress spontaneously if the patient remains stable and shows no evidence of infection. It has a high success rate in patients with first-trimester incomplete miscarriage, with up to 53% of patients having complete expulsion of POC within 1 week without additional medical or surgical treatment, compared to 30% of asymptomatic patients with embryonic demise.[19]  A Cochrane review found that expectant and medical management were equally effective.[5] However, with an expectant approach, it may take longer for POC to be expelled. Other methods should be offered when the patient decides not to continue expectant management.[19] Therefore, ACOG states that "there is insufficient evidence to support or refute the use of misoprostol among women with incomplete pregnancy loss."[4] (A1)

If medical management is selected, ACOG recommends vaginal misoprostol 800 mcg once initially, with a potential second dose between 3 hours and 7 days later.[4] The World Health Organization prefers misoprostol regimens of 400 mcg sublingually once or 600 mcg orally only once for pregnancies <14 weeks of gestation.[7] One large study of women with incomplete abortion showed that the rate of complete abortion within 14 to 28 days of initial treatment with misoprostol without surgical intervention was 96.2%.[24](A1)

With either approach, patients should be counseled to expect heavy bleeding and cramping, often greater than what is experienced with typical menses.[4] Symptoms tend to improve after the POC have been expelled, though some scant to moderate bleeding may last for several weeks. All patients should be instructed to seek medical care if they are soaking 2 pads per hour for ≤2 consecutive hours or if they develop dizziness, lightheadedness, or a fever.[4]

Appropriate analgesics should also be offered. Nonsteroidal anti-inflammatory drugs (NSAIDs) and acetaminophen or paracetamol are typically considered first-line agents, though some patients may require additional medications for a short time. Unless there is an infection, antibiotics are not indicated.

Patients should also have a follow-up plan to ensure the safe completion of the miscarriage. NICE guidelines recommend instructing the patient to take a home urine pregnancy test 3 weeks after bleeding and pain resolve and to return for evaluation if it is positive or if symptoms do not resolve after 2 weeks of expectant management. ACOG states a scheduled follow-up appointment with a repeat ultrasound to ensure complete expulsion of the gestational sac or serial serum β-hCG measurements in areas where ultrasound is unavailable should be performed. Patients with persistent POC, despite expectant or medical management, should be offered surgical management.[4][23](B2)

Surgical Management

Surgical management for incomplete pregnancy loss is indicated in patients with hemodynamic instability, those at high risk for hemorrhage or with septic miscarriages, and people who failed expectant or medical management.[4] Additionally, surgical management is also preferred in those who cannot tolerate large drops in hemoglobin (eg, severe anemia, certain cardiovascular diseases). Results from a randomized controlled trial of 652 women with early pregnancy failure showed that when compared to surgical management, medical management was associated with heavier and more prolonged bleeding and a higher risk of a drop in hemoglobin >2 g/dL.[25] Surgical management is typically considered "definitive treatment" and, if selected, can be accomplished via uterine aspiration or suction curettage in either an operating room or, if clinically appropriate, an outpatient setting under local anesthesia. A dose of prophylactic antibiotics, doxycycline 200 mg intravenously once 1 hour before the procedure, is typically recommended.[4](A1)

Rh(D)-immune Globulin

Rh(D)-immune globulin can be given to Rh-negative patients to prevent alloimmunization. Its use is consistently recommended after surgical management but is more controversial with expectant or medical management of pregnancy loss in the first trimester. 

ACOG states, "Although the risk of alloimmunization is low, the consequences can be significant, and administration of Rh(D)-immune globulin should be considered in cases of early pregnancy loss, especially those later in the first trimester."[25] In many places throughout the US, universal prophylaxis is standard, even in the first trimester. In the UK, NICE guidelines explicitly recommend against its use after expectant or medical management of miscarriage before 12 weeks of gestation.[23] Conversely, the British Committee for Standards in Haematology (BCSH), supported by the Royal College of Obstetricians and Gynaecologists (RCOG), does consider its use appropriate before 12 weeks when uterine bleeding is "repeated, heavy, or associated with abdominal pain," which would be the case in almost all patients with incomplete miscarriage.[26] Given these varying recommendations, regional and institutional protocols should guide management, if available.(A1)

A dose of Rh(D)-immune globulin 50 to 120 mcg intramuscularly once in the first trimester is typically recommended. After 12 weeks of gestation, ACOG guidelines recommend a dose of 300 mcg intramuscularly once, though the guidelines of some other countries recommend lower doses depending on the situation.[27][26]

Differential Diagnosis

In addition to incomplete miscarriage, the differential diagnosis for vaginal bleeding in pregnancy includes:

• Ectopic pregnancy
• Complete miscarriage
• Threatened miscarriage
• Subchorionic hemorrhage or hematoma
• Molar pregnancy
• Nonobstetric bleeding (eg, vaginal or cervical trauma, malignancy, or polyps)
• Infection of the vagina or cervix (eg, candidiasis, bacterial vaginosis, and Chlamydia trachomatis)[28] 
• Septic abortion
• Hemorrhagic shock
• Cervical shock
• Uterine rupture[29]

Prognosis

Patients with incomplete pregnancy loss typically have a very good prognosis with expectant management; approximately 90% of patients have complete expulsion of POC within 4 weeks.[2] The prognosis with medical management is similar.[5] Surgical management is considered "definitive treatment," and similar to expectant and medical management, the prognosis is also excellent. Future fertility does not appear to be impacted. It is safe to attempt conception immediately following a miscarriage. Studies have shown that live birth rates are higher for conceptions occurring within the first 3 months following a pregnancy loss than those who postpone conception.[30][31]

Complications

The risk of complications appears similar across management strategies.[4] The primary complications of incomplete pregnancy loss in the first trimester include retained POC, hemorrhage potentially requiring a blood transfusion, disseminated intravascular coagulation, endometritis, and sepsis.[17] The risk of infection appears higher in low-income compared to high-income countries. If an infection develops, the provider should consider the possibility of a polymicrobial infection of retained POC, typically due to genital flora.[32] The risk of death, while possible, is negligible for uncomplicated miscarriages before 12 weeks. 

Patients may experience some adverse reactions to medical management, most commonly nausea, vomiting, and diarrhea.[33] Surgical management may be complicated by uterine perforation and anesthesia reactions. Limited evidence also suggests that surgical management may increase the risk of intrauterine adhesions, though this is more likely after sharp curettage or repeated procedures.[34] The risk of complications is also generally higher with second-trimester losses, including risks for hemorrhage, infection, cervical laceration, and pulmonary embolism with medical and surgical approaches to management. Although rare, uterine rupture has also been reported with medical management of losses in the second trimester.[6]

One rare complication unique to incomplete miscarriage is cervical shock. With cervical shock, POC within the cervical canal can lead to excessive vagal stimulation, resulting in bradycardia and hypotension that does not respond to IV fluids.[35] In this situation, the POC should be immediately removed from the cervix, which can usually be accomplished easily using ring forceps or a similar type of instrument during a speculum exam; transfer to the operating suite and sedation are not necessary in most cases and may instead delay this definitive treatment.[35]