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Age: 37

Sex: Female

Indication: Pregnant, pelvic pain

LMP: 7 weeks prior

Beta-hCG: 16,000 mIU/mL

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Case #21


Findings

  • Scar in the anterior lower uterine segment, likely related to prior C-section
  • Intrauterine gestational sac within the lower uterine segment scar with very little tissue overlying the anterior margin of the gestational sac
  • Mean sac diameter is 12 mm
  • A fetal pole is present with crown-rump length measuring 8 mm
  • Cardiac contractions are present with heart rate measured at 125 beats/minute
  • Small subchorionic hemorrhage
  • Normal appearance of the ovaries
  • No free fluid in the cul-de-sac


Diagnosis

C-section scar ectopic pregnancy

Sample Report

Single live gestation with gestational sac located in a scar in the anterior wall of the lower uterine segment, concerning for a C-section scar ectopic. Recommend obstetric evaluation. Gestational age is estimated at 6 weeks, 5 days by crown-rump length.


Discussion

  • C-section scar ectopic pregnancies are rare and typically present in the first trimester with vaginal bleeding (though they can sometimes present in the second trimester)
  • Worry about this diagnosis if you see implantation in the lower uterine segment in a patient with a history of a prior C-section
  • C-section scar ectopic pregnancies grow into the myometrium and cause thinning of the anterior uterine wall, which can lead to catastrophic uterine rupture
  • Another diagnosis to consider if you see a gestational sac in the lower uterine segment is a spontaneous abortion in progress, though in this case, the gestational sac will be located in the endometrial canal instead of the uterine wall, the gestational sac is usually abnormal in appearance, and the embryo is often no longer alive
  • In ambiguous cases, short interval followup ultrasound can help differentiate spontaneous abortion in progress (which should change location) from a C-section scar ectopic (which will not change location)


Images

Gestational sac located within the C-section scar in the anterior wall of the lower uterine segment (red arrow) with overlying mural thinning (yellow arrow).

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