This patient presents with a heterotopic pregnancy (HP): that is, an intrauterine pregnancy plus a concurrent ectopic pregnancy. She was currently undergoing fertility treatment and had been taking clomiphene (Clomid®) to induce ovulation.
The findings on this scan that suggest heterotopic pregnancy are the intrauterine pregnancy (IUP) and empty extrauterine gestational sac seen as a hyperechoic ring posterior-lateral to the uterus. The free fluid in the right upper quadrant is identified by the hypoechoic stripe in Morison’s Pouch, suggesting a ruptured HP.
Spontaneous heterotopic pregnancy without fertility treatment is rare, with an estimated incidence of 1/20,000. This allows the sonographer to essentially rule out ectopic pregnancy if a clear IUP is identified.
Clomid increases the risk of HP to 1/900, while in-vitro fertilization dramatically increases the risk to ~1/100 or higher depending on the number of transferred embryos.1,2 Other fertility treatments have been associated with HP, including Gamete and Zygote Intrafallopian Tube Transfer (GIFT/ZIFT).3
Patients who are undergoing fertility treatment and present with signs or symptoms of ectopic pregnancy should be considered to have a HP until proven otherwise.
Transvaginal ultrasound has been shown to be 92% sensitive and 100% specific for the detection of HP in a recent study.4 This is quite similar to the sensitivity for a typical ectopic pregnancy.
Ultrasound findings suggestive of HP are an intrauterine gestational sac plus “(1) an inhomogeneous adnexal mass; (2) an empty extrauterine gestational sac seen as a hyperechoic ring; or (3) a yolk sac and/or fetal pole with or without cardiac activity in an extrauterine sac.”4
The adnexa should be carefully visualized in all pregnant patients, even if an IUP is identified.
It is common for there to be discordance in visibility of fetal cardiac activity between the IUP and ectopic pregnancy.
Bello GV, Schonholz D, Moshirpur J, Jeng DY, Berkowitz RL. Combined pregnancy: the Mount Sinai experience. Obstet Gynecol Surv. 1986;41(10):603-13. [pubmed]
Dor J, Seidman DS, Levran D, Ben-rafael Z, Ben-shlomo I, Mashiach S. The incidence of combined intrauterine and extrauterine pregnancy after in vitro fertilization and embryo transfer. Fertil Steril. 1991;55(4):833-4. [pubmed]
Wang YL, Yang TS, Chang SP, Ng HT. Heterotopic pregnancy after GIFT managed with expectancy: a case report. Zhonghua Yi Xue Za Zhi (Taipei). 1996;58(3):218-22. [pubmed]
Li XH, Ouyang Y, Lu GX. Value of transvaginal sonography in diagnosing heterotopic pregnancy after in-vitro fertilization with embryo transfer. Ultrasound Obstet Gynecol. 2013;41(5):563-9. [pubmed]
Condous G, Okaro E, Khalid A, et al. The accuracy of transvaginal ultrasonography for the diagnosis of ectopic pregnancy prior to surgery. Hum Reprod. 2005;20(5):1404-9. [pubmed]