Recent advances in ultrasound diagnostic capability have enabled earlier detection of ectopic pregnancy, increasing the number of cases suitable for less invasive methotrexate (MTX) or laparoscopic intervention. We report here a case of interstitial pregnancy ultimately resolved through laparoscopic access after attempted MTX treatment.
  A diagnosis of right interstitial pregnancy was made at seven weeks, when a placental sac and viable embryo (with heartbeat) were detected near the right fallopian tubal horn. Findings were confirmed by MRI, so systemic MTX (1 mg/kg intramuscularly) was given. Although urinary hCG thereafter declined from 45,048 IU/L to 24,151 IU/L, heart tones persisted, and both embryonic crown-rump length and placental sac showed continued growth. At Week 9 of pregnancy, a laparoscopically facilitated right interstitial incision was made, exposing the implantation site. The extremely attenuated tubal wall was then incised linearly, allowing extraction of the intact sac and villi. Once discharged from the hospital, the patient's urinary hCG levels decreased steadily.
  It has been reported that even with detectable embryonic heartbeat or very elevated hCG, the success rate of conservative MTX therapy with interstitial pregnancy is high. However, if the placental sac expands without loss of heartbeat, surgical intervention at an early stage should be considered.