First trimester abortion

(Redirected from Spontaneous abortion)

See Vaginal bleeding in pregnancy (less than 20wks) for diagnostic approach to early vaginal bleeding in pregnancy.


  • Estimates are up to 15% of pregnancies end in a 1st trimester abortion, usually due to fetal chromosomal abnormalities
  • Primary risk factors include history of prior miscarriage and advanced maternal age[1]
    • Other risk factors include heavy alcohol use, uterine structure abnormalities, and systemic maternal disease

Abortion Types

Classification Characteristics OS Fetal Tissue Passage Misc
Threatened Abdominal pain or bleeding; < 20 weeks gestation Closed No If < 11 weeks (with fetal cardiac activity) 90% progress to term. If between 11 and 20 weeks 50% progress to term
Inevitable Abdominal pain or bleeding; < 20 weeks gestation Open No
Incomplete Abdominal pain or bleeding; < 20 weeks gestation Open Yes, some
Complete Abdominal pain or bleeding; < 20 weeks gestation Closed Yes, complete expulsion of products Distinguish from ectopic based on decreasing hCG and/or decreased bleeding
Missed Fetal death at <20 weeks without passage of any fetal tissue for 4 weeks after fetal death Closed No
Septic Infection of the uterus during a miscarriage. Most commonly caused by retained products of conception Open No, or may be incomplete Uterine tenderness and purulent discharge from the OS may be present

Clinical Features

  • Visualize any clots or bleeding from external os
  • Assess internal os as open or closed based on ability to pass finger through os
  • Pregnancy ≤ 13 weeks

Differential Diagnosis

Vaginal Bleeding in Pregnancy (<20wks)



  • RhoGam if Rh Negative
    • Based off of Level C recommendation from ACOG for threatened abortion (risk of alloimmunization is low, but consequences can be significant). Specifically state it should be considered. Best course of action is to discuss this with your hospital's OB team, most will recommend it.
  • IVF and/or PRBCs if severe bleeding
  • Misoprostol only for < 12 weeks gestation: give 800mcg vaginally, dose can be repeated once within 7 days if no response [2]
    • If available, mifepristone 200mg PO should be given 24 hours prior to first dose of misoprostol (NNT = 6)
    • Supportive care with anti-emetic and NSAIDs for misoprostol side effects
  • D&C and OB/gyn consult may be necessary if medical management fails or continuous products/vaginal bleeding > 7-14 days


  • Discharge Criteria
    • After brief period of observation and if hemodynamically stable
    • Discharge w/ pain medications and close OB follow-up for repeat ultrasound
    • Give strict return precautions (heavy vaginal bleeding, worsening pain, or fever)
  • Admission Criteria
    • If hemodynamically unstable, septic, or suspect gestational trophoblastic disease/ectopic pregnancy
    • Urgent OBGYN consult if active hemorrhage and need for Dilation and Curettage

See Also

External Links


  1. Maconochie N, Doyle P, Prior S, Simmons R. Risk factors for first trimester miscarriage--results from a UK-population-based case-control study. BJOG. 2007;114(2):170–186. doi:10.1111/j.1471-0528.2006.01193.x
  2. ACOG Practice Bulletin Update. Early Pregnancy Loss. November 2018.