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Updated: Sep 7 2022

Spontaneous Abortion
  • A 35-year-old G3P2 at 12 weeks of gestation presents to the emergency department with 6 hours of vaginal bleeding and cramping pain. She has had 2 prior vaginal deliveries and no history of pregnancy-related complications. She has been receiving regular prenatal care. A transvaginal ultrasound was performed and showed a fetus without cardiac activity in the lower uterine segment. (Inevitable abortion) 
  • Overview
    • non-elective termination of pregnancy at < 20 weeks gestation
  • Epidemiology
    • incidence
      • occurs spontaneously in 15% of all pregnancies
    • demographics
      • more common in women of advanced maternal age (age > 35 years)
        • ~11% risk in women < 35 years old
        • 17% in women 35-39 years old
        • 33% in women 40-44 years old
        • 57% risk in women ≥45 years old
    • risk factors
      • advanced maternal age (> 35 years old)
        • number 1 risk factor due to strong association with fetal chromosomal abnormalities
      • advanced paternal age
      • prior pregnancy loss
        • risk increases as number of prior miscarriages increase
      • maternal diabetes
        • type I or type II diabetes
        • gestational diabetes begins > 20 weeks, so cannot contribute to spontaneous abortion
      • obesity
      • thyroid disease
        • hypo- or hyperthyroidism
      • stress
        • acute or chronic
      • inherited thrombophilias
      • conception < 3 months after live birth
      • pregnancy with IUD in place
      • subchorionic hematoma
  • Etiology
    • fetal chromosomal abnormalities
      • present in up to 70% of spontaneous abortions
    • infection
      • listeria
      • parvovirus B19
        • 5.6x higher risk of pregnancy loss if infection occurs in first trimester
      • syphilis
      • cytomegalovirus (CMV)
    • incompetent cervix 
    • uterine abnormalities
      • leiomyomas (fibroids) 
      • polyps
      • adhesions
      • septa
    • trauma 
      • direct impact to uterus
      • violent
        • gunshot wounds
        • penetrating injuries
        • blunt abdominal trauma
      • iatrogenic
        • chorionic villus sampling 
        • amniocentesis 
    • toxins, radiation, and environmental exposures
    • medications and substance abuse
      • risk increases in dose-related fashion
      • alcohol
      • smoking
      • cocaine and methamphetamines
  • Prognosis
    • very good if patient if properly treated
    • risk of future miscarriage natural history of disease
      • 14% risk of future miscarriage after 1 miscarriage
      • 26% after 2 miscarriages
      • 28% after 3 miscarriages
Types of Spontaneous Abortions
Vaginal Bleeding Passage of Contents Cervical Os Ultrasound
Threatened    Yes
No Closed Fetus present and has cardiac activity
Inevitable  Yes No Open Fetus present
Incomplete  Yes Yes Open Retained fetal parts
Complete  Yes Yes Closed No fetus present
Missed No No Closed Fetus present but does not have cardiac activity


  • Symptoms 
    • vaginal bleeding
      • commonly occurs in first trimester without subsequent loss of pregnancy
    • abdominal/pelvic cramping pain
    • asymptomatic 
    • may note reduction in previous pregnancy symptoms 
      • decreased nausea 
      • decreased breast tenderness 
  • Physical exam 
    • vitals
      • may exhibit signs of shock if significant hemorrhage
    • speculum exam 
      • assess source and quantity of bleeding 
      • bleeding from cervix and open cervical os suggest spontaneous abortion 
      • significant hemorrhage should prompt urgent evaluation and intervention 
    • bimanual exam 
      • determine whether cervix is open 
      • assess presence of tissue within cervical canal 
      • can estimate gestational age 
    • handheld Doppler 
      • listen for fetal heart tones 
      • absence of fetal heart ones in pregnancy ≥ 12 weeks suggests potential early pregnancy loss 
  • Transvaginal ultrasound post
    • indications
      • key for diagnosis of spontaneous abortion
      • assessment of fetal cardiac activity
    • findings
      • looking for presence of intrauterine gestation and evidence of viability
      • diagnosis of spontaneous abortion if any one of the following
        • gestational sac ≥ 25 mm without yolk sac or embryo
        • embryo with crown rump length ≥ 7 mm that does not have cardiac activity
        • following a pelvic ultrasound that showed a gestational sac without a yolk sac
          • absence of an embryo with a heartbeat in ≥ 2 weeks
        • following a pelvic ultrasound that showed a gestational sac with a yolk sac
          • absence of an embryo with a heartbeat in ≥ 11 days
    • may begin with transabdominal ultrasound, but proceed to transvaginal ultrasound if unable to demonstrate cardiac activity in an intrauterine pregnancy
  • Hysterosalpingogram  
    • indications
      • can elucidate potential cause of spontaneous abortion
      • only performed after treatment for confirmed spontaneous abortion
    • findings
      • uterine structural abnormalities
  • Serum β-hCG
    • not required for diagnosis
    • useful in specific circumstances
      • to determine concern for ectopic pregnancy if gestational sac not seen on ultrasound
      • if ultrasound not available
    • drop in β-hCG >25% over 48 hours in setting of uterine bleeding highly suggestive of early pregnancy loss
  • Serum progesterone
    • low levels (<3 5 nmol/L) associated with early pregnancy loss
    • cannot use for definitive diagnosis due to high variability of normal levels among pregnancies
  • Normal intrauterine pregnancy
    • key distinguishing factors
      • serial ultrasounds demonstrate viable intrauterine gestation
      • can have cramping and vaginal bleeding in normal pregnancy
  • Ectopic pregnancy 
    • key distinguishing factors
      • ultrasound findings
        • no intrauterine pregnancy visible
        • may see visible pregnancy that is outside the uterine cavity
        • may see bleeding in the pelvis (suggestive of ruptured ectopic)
      • may have abnormal β-hCG levels
  • Hydatidiform mole 
    • key distinguishing factors
      • ultrasound findings
        • enlarged uterus
        • “snowstorm” appearance of uterus
      • abnormally elevated β-hCG
  • Expectant management
    • counseling and return precautions
      • indications
        • < 14 weeks of gestation
        • threatened or inevitable abortion  
        • stable vital signs
        • no evidence of infection
        • desire to avoid surgery and/or medication
        • desire to pass uterine contents at home
      • majority of expulsions occur in first two weeks after diagnosis
      • if unsuccessful after four weeks then proceed to surgical evaluation
  • Medical
    • misoprostol
      • indications 
        • women with nonviable pregnancy up to 12 weeks + 6 days of completed gestation 
        • hemodynamically stable 
        • no evidence of hemorrhage, severe anemia, bleeding disorders 
        • no evidence of infection 
        • can be used in second trimester treatment in hospital setting 
      • modalities 
        • administered vaginally as single dose 
        • repeat dose in seven days if no response to first dose 
    • mifepristone 
      • indications 
        • pretreatment prior to misoprostol 
          • preferred method for first trimester spontaneous abortion 
      • modalities 
        • single oral dose followed 24 hours later by single dose of intravaginal misoprostol  
    • rhoGAM 
      • indications  
        • all Rh(D)-negative mothers if father is Rh(D)-positive or unknown 
      • modalities 
        • single intramuscular or intravenous dose 
  • Surgical
    • dilation and curettage (D&C)
      • indications 
        • incomplete, inevitable, or missed abortion 
        • first trimester or early second trimester (< 16 weeks gestation) 
        • failed expectant or medical management 
      • modalities 
        • dilation of cervix and removal of pregnancy with sharp curettage and/or suction curettage
    • dilation and evacuation (D&E)
      • indications
        • ≥ 16 weeks gestation 
      • modalities
        • wide mechanical dilation of cervix with destruction of fetal parts and removal of tissue with large-bore vacuum curette
    • hysteroscopic removal
      • indications
        • retained products of conception after failed expectant, medical, or surgical management
        • no signs of hemorrhage
        • no signs of infection
      • modalities
        • scope used to visualize abnormal tissue
        • abnormal tissue removed with morcellator or grasper
  • Follow-up
    • weekly serum β-hCG
      • after expectant or medical management
      • continue to measure until serum β-hCG undetectable
  • Hemorrhage
    • can occur during spontaneous abortion or during/after surgical treatment
    • could lead to maternal death
    • risk factors
      • uterine atony after surgical treatment
      • cervical injury
      • uterine perforation
      • subinvolution of placental implantation site
      • underlying coagulopathy
    • treatment
      • check for/remove any retained products of conception
      • uterotonics for uterine atony
        • oxytocin
        • misoprostol
      • surgical treatment of cervical injury or uterine perforation
      • intravenous (IV) fluids and blood products if hemodynamically unstable
  • Retained products of conception
    • suspect in patients with
      • uterine bleeding that increases in volume
      • uterine bleeding that persists > 2 weeks after uterine evacuation
    • treatment
      • IV fluids and blood products if hemodynamically unstable
      • urgent surgical intervention
  • Endometritis
    • presentation
      • mild uterine tenderness
      • empty uterus on ultrasound exam
      • +/- fever
      • occurs after complete spontaneous abortion or uterine evacuation
    • treatment
      • oral broad-spectrum antibiotics
  • Septic abortion
    • spontaneous abortion accompanied by intrauterine infection
    • risk factors
      • induced abortion (as opposed to spontaneous abortion) 
      • retained products of conception
    • treatment
      • IV fluids and blood products if hemodynamically unstable
      • obtain blood and endometrial cultures
      • IV broad-spectrum antibiotics
        • give until afebrile for 48 hours
      • oral antibiotics
        • give for 10-14 days after completion of IV antibiotic course
      • surgical evacuation of any retained products of conception
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