- Separation of products of conception from the uterus prior to the potential for fetal survival outside the uterus
- Spontaneous abortion (SAb):
- Expulsion or extraction from the uterus of an embryo or fetus weighing ≤500 g
- Threatened abortion:
- Vaginal bleeding early in pregnancy without dilatation of the cervix, rupture of the membranes, or expulsion of products of conception
- Inevitable abortion:
- Cervical dilatation, rupture of membranes, or expulsion of products in the presence of vaginal bleeding
- Complete abortion:
- Entire contents of uterus expelled; common before 12 weeks’ gestation
- Incomplete abortion:
- Abortion with retained products of conception, generally placental tissue; more common after 12 weeks’ gestation
- Missed abortion:
- In utero death of embryo/fetus prior to 20 weeks’ gestation; products of conception retained
- Induced abortion:
- Evacuation of uterine contents or products of conception medically or surgically
- Septic abortion:
- Common complication of illegally performed induced abortions; a spontaneous or therapeutic abortion complicated by pelvic infection
- Habitual spontaneous abortion:
- 2 or more consecutive pregnancy losses at <15 weeks’ gestation
- Synonym(s): Miscarriage; Habitual abortion; Recurrent abortion; Involuntary pregnancy loss
Predominant age: Increases with advancing age, especially >35 years; at age 40, the loss rate is twice that of age 20
- ∼8–20% of all clinically recognized pregnancies end in spontaneous abortion, 80% of these in the first 12 weeks.
- When both clinical and biochemical (B-HCG detected) pregnancies are considered, up to 50% of pregnancies end in spontaneous abortion.
Most cases of spontaneous abortion occur in patients without identifiable risk factors; however, risk factors listed in order of importance include:
- Chromosomal abnormalities
- Advancing maternal age
- Uterine abnormalities
- Maternal chronic disease (diabetes mellitus, polycystic ovarian syndrome, systemic lupus erythematosus, hypertension, antiphospholipid antibodies, thyroid disease, renal disease)
- Other possible contributing factors include smoking, alcohol, infection, and luteal phase defect, although conclusive data are currently lacking.
∼50–65% of 1st-trimester spontaneous abortions have significant chromosomal anomalies, with 1/2 of these being autosomal trisomies and the remainder being triploidy, tetraploidy, or 45X monosomies.
- Progestogens: Currently, there is no evidence that routine use of oral or IM progestogens prevents miscarriage in early to mid-pregnancy. However, there is some evidence that women with a history of recurrent miscarriage may benefit from this type of treatment (1)[A].
- Immunotherapy: No current evidence to support use of immunotherapy in patients with a history of recurrent miscarriage (2)[A]
- Chromosomal anomalies
- Congenital anomalies
- Maternal factors: Uterine abnormalities, infection (toxoplasma, other viruses, rubella, cytomegalovirus, herpesvirus), maternal endocrine disorders, hypercoagulable state
- Consider any reproductive-age woman with vaginal bleeding to be pregnant until proven otherwise.
- Vaginal bleeding:
- Characteristics (amount, color, consistency, associated symptoms), onset (abrupt or gradual), duration, intensity/quantity, and exacerbating/precipitating factors
- Abdominal pain/uterine cramping
- Rupture of membranes
- Passage of products of conception
- Prenatal course: Toxic or infectious exposures, family or personal history of genetic abnormalities, past history of ectopic pregnancy or spontaneous abortion, endocrine disease, autoimmune disorder, bleeding/clotting disorder
- Any pregnant woman with vaginal bleeding needs immediate evaluation.
- Estimate hemodynamic stability:
- Obtain orthostatic vital signs.
- Abdominal exam for tenderness (SAb), guarding, rebound, bowel sounds (peritoneal signs more likely seen with ectopic pregnancy)
- Pelvic exam for cervical dilation, blood, products of conception, uterine size/tenderness
Diagnostic Tests & Interpretation
Initial lab tests
- Urine human chorionic gonadotropin (HCG)
- Complete blood count
- Rh type
- Cultures: Gonorrhea/chlamydia
- Serial serum HCG measurements can assess viability of the pregnancy. Serum HCG should rise at least 67% every 48 hours in early pregnancy.
HCG levels are particularly useful in cases where an intrauterine pregnancy (IUP) has not been documented by ultrasound.
- In the case of vaginal bleeding with no documented IUP, follow serum HCG levels weekly to zero to ensure complete expulsion of all products of conception.
- If levels plateau, suspect ectopic pregnancy or retained products of conception.
- Ultrasound (US) exam to evaluate fetal viability and to rule out ectopic pregnancy:
- HCG >2,000 U/L necessary to detect IUP via transvaginal US (TVUS), >6,500 U/L for abdominal ultrasound
- TVUS criteria for nonviable intrauterine gestation include 5-mm fetal pole without cardiac activity or 16-mm gestational sac without a fetal pole.
Follow-Up & Special Considerations
- If initial HCG level does not permit documentation of IUP by TVUS, follow serum HCG in 48 hrs to ensure appropriate rise.
- Follow HGC and repeat US once HCG at a level commensurate with visualization on US (see above).
- Provide patient with ectopic precautions in interim.
- Fetal heart tones can be auscultated with Doppler starting between 10–12 weeks’ gestation from last menstrual period for a viable pregnancy.
- 90–96% of pregnancies with fetal cardiac activity and vaginal bleeding at 7–11 weeks’ gestation result in continued pregnancy.
Products of conception, placental villi
- Ectopic pregnancy: Potentially life-threatening; must be ruled out with US in any woman of childbearing age with abdominal pain and vaginal bleeding
- Cervical polyps, neoplasias, and/or inflammatory conditions can cause vaginal bleeding.
- Hydatidiform mole pregnancy
- HCG-secreting ovarian tumor
- Physiologic bleeding in normal pregnancy (implantation bleeding)
- Long-term conception rate and pregnancy outcomes are similar for women who undergo medical or surgical evacuation.
- Postinfection rates lower with medical vs surgical management
- Misoprostol: Most common agent for inducing passage of tissue in missed or incomplete abortion:
- Not approved by Food and Drug Administration for treatment of early pregnancy failure
- Efficacy: Complete expulsion of products of conception in 71% by day 3, 84% by day 8
- Efficacy depends on route of administration, gestational age of pregnancy, and dose
- Recommended dose 800 µg vaginally (3)[A]; alternate regimens exist including World Health Organization regimen of 800 µg vaginally or 600 µg sublingually q.3 hours for up to 3 doses; multidose regimens and oral dosing may result in increased side effects
- Common adverse effects include abdominal pain/cramping, nausea, and diarrhea. Pain increases at higher doses, but manageable with analgesia. No increase in nausea/diarrhea with higher dose.
- Recommended for stable patients who decline surgery but do not want to wait for spontaneous passage of products of conception
Rh-negative patients should be given Rh immune globulin following spontaneous abortion (4)[C].
Issues for Referral
Complementary and Alternative Medicine
- Uterine aspiration (dilation and curettage or via vacuum aspiration) is the conventional treatment.
- Indications: Septic abortion, heavy bleeding, hypotension, patient choice
- Risks: Anesthesia, uterine perforation, intrauterine adhesions, cervical trauma, infection that may lead to infertility or increased risk of ectopic pregnancy
- Surgical intervention leads to fewer days of vaginal bleeding, with a lower risk of incomplete abortion and heavy bleeding. It does carry a higher risk of infection (7)[A].
- Vacuum aspiration may be less painful than dilatation and curettage (D & C), and does not require general anesthesia (8)[B].
- Data from induced abortions suggests that antibiotic prophylaxis with doxycycline 100 mg b.i.d. substantially reduces postprocedure infection risk; however, data for incomplete abortions treated surgically is inconclusive (9)[A].
- For patients who desire contraception after completion of a spontaneous abortion, immediate insertion of an intrauterine device is acceptable and safe (10)[A].
- Identification of products of conception within material expelled from the uterus or D & C specimen (important to distinguish villi and sac from decidua)
- If abortion is complete, observe the patient for further bleeding.
- Pelvic rest until 2 weeks after evacuation
- If spontaneous abortion occurs in setting of previously documented IUP and abortion is completed with resumption of normal menses, it is not necessary to check or follow serum HCG to 0.
- If bleeding ceases, prognosis is excellent.
- Habitual abortion:
- Prognosis depends on etiology.
- Prognosis is still excellent, with up to 70% rate of success with subsequent pregnancy.
- Potential complications of D & C include uterine perforation, bleeding, adhesions, cervical trauma, infection that may lead to infertility, or increased risk of ectopic pregnancy.
- Retained products of conception
- Psychological morbidity, including depression, anxiety, feelings of guilt
- 632 Missed abortion
- 634.90 Spontaneous abortion, unspecified, without mention of complication
- 640.03 Threatened abortion, antepartum
- 637.90 Legally unspecified type of abortion, unspecified, without mention of complication
- 637.00 Unspecified type of abortion, unspecified, complicated by genital tract and pelvic infection
- 17369002 Spontaneous abortion (disorder)
- 16607004 Missed abortion (disorder)
- 54048003 Threatened abortion (disorder)
- Any reproductive-age woman or pregnant woman with abdominal pain and vaginal bleeding must be evaluated. Ectopic pregnancy must be ruled out, and hemodynamic stability should be ensured.
- Patient preference should determine whether management is medical, expectant, or surgical, as all options have similar long-term outcomes.
- Assessment of psychological symptoms after spontaneous abortion should be an integral part of follow-up visits, with counseling, medication, and referral as appropriate.
- Patients and their partners should be reassured that there are no known interventions to prevent spontaneous abortion, and should be provided with appropriate medical explanations to reduce anxiety and guilt.