Basics
Description
Spontaneous abortion (SAB), or miscarriage, is the spontaneous loss of a pregnancy prior to 20 weeks gestation.
- 15% of clinically recognized pregnancies end in miscarriage.
- Up to 30-45% of unrecognized pregnancies end in miscarriage.
- Most SABs (80%) occur in the first trimester with the incidence decreasing with increasing gestational age.
Risk Factors
There are many recognized risk factors for SAB.
- Advancing maternal age
- The prevalence of miscarriage in women under 20 is 12% compared to >25% in women over 40 years of age.
- Prior miscarriage
- The risk of another miscarriage is 20% after one SAB, 28% after two, and 43% after three.
- Alcohol
- Moderate alcohol consumption (>3 drinks/week) increases the risk of SAB, especially in the first 10 weeks of pregnancy.
- Cocaine
- Cigarette smoking
- Caffeine
- There is a modest increase in the rate of SAB in women who drink more than 4 cups of coffee (or other caffeine-containing beverages) per day.
- NSAID use
- If used at or around conception, NSAID use increases the incidence of miscarriage.
Pathophysiology
- Threatened abortion is uterine bleeding from a gestation of <20 weeks without any cervical dilatation or effacement.
- Incomplete abortion is the passage of some but not all placental tissue through the cervix before 20 weeks gestation.
- Inevitable abortion is uterine bleeding from a gestation of <20 weeks accompanied by cervical dilatation, but without expulsion of any placental or fetal tissue through the cervix.
- Completed abortion occurs when all products of conception have been expelled before 20 weeks gestation.
- Missed abortion occurs when fetal expulsion does not occur despite intrauterine fetal demise <20 weeks gestation.
- Septic abortion is any type of abortion associated with fever, chills, pain, and purulent uterine discharge.
Etiology
There are numerous causes of SAB.
- Fetal:
- Chromosomal abnormalities
- Half of SABs are caused by karyotype abnormalities.
- Most of these abnormalities occur de novo and are not inherited.
- Maternal:
- Endocrinopathies
- Hyperandrogenism
- Hyperprolactinemia
- Poorly controlled diabetes
- Hypercoagulable disorders
- Systemic lupus erythematosus
- Antiphospholipid syndrome
- Factor V Leiden
- Trauma
- Maternal anatomic defects
- Infection
- Rubella
- Primary herpes simplex infection
- Toxoplasmosis
- Listeria monocytogenes
- CMV
- Anatomic
- Leiomyomas
- Cervical insufficiency
- Intrauterine adhesions
Associated Conditions
Recurrent SAB - 3 or more consecutive miscarriages
Diagnosis
History/Management
- Is there a history of previous miscarriage?
- What is the gestational age?
- Has the patient passed any blood clots or recognizable products of conception?
- Has she recently been ill?
- Has she been taking any medications or using any illicit substances?
- Has there been any trauma to the abdomen or pelvis?
- Signs and symptoms:
- Vaginal bleeding is the most common symptom reported in women with SAB.
- Occurs in up to 40% of all pregnant women and half of these will end up being SABs.
- May be painful or painless.
- Abdominal or pelvic pain
- Fever or chills
- Prior symptoms of pregnancy (nausea, vomiting, breast tenderness, fatigue) may disappear.
Physical Exam
- Temperature, heart rate, blood pressure
- A speculum exam should be performed to locate the source of bleeding.
- On bimanual exam, assess if the cervix is open or closed, if the uterus is boggy or tender.
Tests
Lab
- Serum human chorionic gonadotropin level may be inappropriately low. This value is not diagnostic; however, unless a quantitative level was previously checked.
- Maternal hemoglobin to assess for potentially harmful blood loss.
- Type and screen to determine (a) maternal blood type and Rh status, and (b) also necessary if there has been significant bleeding and there is a likelihood of transfusion.
- Blood cultures and cervical cultures if septic abortion is suspected.
- Any tissue that patient has passed at home or in hospital should be sent to pathology to assess for chorionic villi and if applicable chromosomal analysis.
Imaging
- Ultrasonography is the most helpful imaging tool in diagnosing SAB.
- Absence of fetal heart activity
- Assessment of the presence/absence/size of the gestational sac, fetal pole, and yolk sac
Differential Diagnosis
Because vaginal bleeding occurs frequently in the first trimester of pregnancy, this symptom does not always signal miscarriage. Other potential etiologies include:
- Implantation bleeding
- Bleeding from other sites in the gynecologic tract
- Ectopic pregnancy
Treatment
Medication
- Misoprostol
- Rh-negative women should be given Rh immune globulin
- 50 μg dose <12 weeks gestation
- Standard 300 μg dose >12 weeks gestation
Additional Treatment
General Measures
- Medical therapy with misoprostol
- Expectant management
- Waiting for the products of conception to pass on their own.
- Most likely to result in complete abortion prior to 6 weeks gestation and after 14 weeks gestation.
- Dilation and curettage
Issues for Referral
- Patients with recurrent abortion may benefit from referral to a genetic specialist.
- Grief counseling may be appropriate.
- A diagnostic evaluation should be initiated in a patient with 1 second-trimester SAB or 2 first-trimester SABs.
Additional Therapies
- Complete abortion does not require further medical therapy, but care should be made to support the patient psychologically.
- Septic abortion requires antibiotics and prompts surgical evacuation.
- Incomplete, inevitable, or missed abortion may be treated expectantly, medically, or surgically, depending on the patient's clinical status.
Surgery
Dilation and curettage with suction curettage is recommended in certain situations, including:
- Septic abortion
- Unsuccessful treatment with misoprostol
- When expectant management has not resulted in expulsion
- In concordance with the patient's wishes
- Heavy bleeding
In-Patient Considerations
Initial-Stabilization
- Assess the patient for hemodynamic stability.
- If the patient is unstable, large-bore IVs should be placed and IV fluids should be started.
Admission Criteria
- Septic abortion
- Heavy bleeding
- Hemodynamic instability
IV Fluids
Lactated ringers and normal saline are appropriate for fluid resuscitation if necessary.
Discharge Criteria
- All products of conception have been expulsed.
- Psychological issues have been addressed.
Ongoing Care
Follow-Up Recommendations
Pelvic rest for 2-4 weeks
Patient Monitoring
- Monitor for prolonged vaginal bleeding
- Monitor psychological state
Prognosis
There is an increased risk of SAB in future pregnancies.
Complications
- When managed properly, SAB is not generally associated with medical complications.
- There may be significant depression associated with the loss of a pregnancy.
- Infection rate of SABs: 1-2%
Additional Reading
1Bagratee JS, Khullar V, Regan L. A randomized controlled trial comparing medical and expectant management of first trimester miscarriage. Hum Reprod. 2004;19:266-271. [View Abstract]2Gibbs RS, Karlan BY, Haney AF Danforth's obstetrics and gynecology, 10th ed. Philadelphia, PA: Lippincott, Williams, and Wilkins, 2008.3Katz VL, Lobo RA, Lentz G Comprehensive gynecology, 5th ed. Maryland Heights, MO: Mosby Elsevier, 2007.
Codes
ICD9
- 634.90 Spontaneous abortion, without mention of complication, unspecified
- 634.91 Spontaneous abortion, without mention of complication, incomplete
- 634.92 Spontaneous abortion, without mention of complication, complete
- 640.01 Threatened abortion, delivered, with or without mention of antepartum condition
- 640.03 Threatened abortion, antepartum condition or complication
- 637.91 Unspecified abortion, without mention of complication, incomplete
- 637.00 Unspecified abortion, complicated by genital tract and pelvic infection, unspecified
- 637.01 Unspecified abortion, complicated by genital tract and pelvic infection, incomplete
- 637.02 Unspecified abortion, complicated by genital tract and pelvic infection, complete
- 632 Missed abortion
ICD10
- O03.4 Incomplete spontaneous abortion without complication
- O03.9 Complete or unsp spontaneous abortion without complication
- O20.0 Threatened abortion
- O03.9 Complete or unsp spontaneous abortion without complication
- O08.0 Genitl trct and pelvic infct fol ectopic and molar pregnancy
- O02.1 Missed abortion
SNOMED
- 17369002 spontaneous abortion (disorder)
- 54048003 threatened abortion (disorder)
- 16863000 incomplete abortion (disorder)
- 59363009 inevitable abortion (disorder)
- 30260009 abortion with sepsis (disorder)
- 16607004 missed abortion (disorder)
Clinical Pearls
- Spontaneous abortion (SAB) is the most frequent complication of pregnancy.
- Advanced maternal age and previous miscarriage are the 2 strongest factors that predict future miscarriage.
- Most SABs are associated with congenital or chromosomal abnormalities.
- Always important to rule out ectopic pregnancy with history, physical examination, laboratory studies, and ultrasound.
- Expectant management is most likely to result in complete abortion prior to 6 weeks gestation and after 14 weeks gestation.
- Once a normal fetal heart rate is visualized on ultrasound, risk of spontaneous abortion is 3%.