In select cases, it is reasonable to observe very early tubal pregnancies that are associated with stable or falling serum �-hCG levels. Mavrelos and coworkers (2013) noted that almost one third of 333 tubal ectopic pregnancies measuring <3 cm and with �-hCG levels < 1500 mIU/mL resolved without intervention. Cohen and associates (20 14b) similarly followed 674 women with declining �-hCG levels to successul resolution. hese findings have been supported by smaller randomized trials Qurkovic, 2017; van Mello, 2013).
With expectant management, subsequent rates of tubal patency and intrauterine pregnancy are comparable with surgical or medical management. That said, compared with the established safety of medical and surgical therapy, the prolonged surveillance and risks of tubal rupture support the practice of expectant therapy only in appropriately selected and counseled women.
An interstitial pregnancy is one that implants within the proximal tubal segment that lies within the muscular uterine wall (Fig. 19-7). Incorrectly, they may be called cornual pregnancies, but this term describes a conception that develops in the rudimentary horn of a uterus with a miillerian anomaly (Moawad, 2010). Risk factors are similar to others discussed for tubal ectopic pregnancy, although previous ipsilateral salpingectomy is a specific risk factor for interstitial pregnancy (Lau, 1999). Undiagnosed interstitial pregnancies usually rupture following 8 to 16 weeks of amenorrhea, which is later than for more distal pregnancies. his is due to greater distensibility of the myometrium covering the interstitial fallopian tube segment. Because of the proximity of these pregnancies to the uterine and ovarian arteries, hemorrhage can be severe and associated with mortality rates as high as 2.5 percent (Tulandi, 2004).
With transvaginal sonography and serum �-hCG assays, interstitial pregnancy can now be diagnosed early in many cases, but diagnosis can be challenging. hese pregnancies sonographically can appear similar to an eccentrically implanted uterine pregnancy, especially in a uterus with a miillerian anomaly. Criteria that may aid diferentiation include: an empty uterus, a gestational sac seen separate from the endometrium and > 1 cm away from the most lateral edge of the uterine cavity, and a thin, < 5-mm myometrial mantle surrounding the sac (Timor-Tritsch, 1992). Moreover, an echo genic line, known as the "interstitial line sign," extending from the gestational sac to the endometrial cavity most likely represents the interstitial portion of the fallopian tube and is highly sensitive and specific (Ackerman, 1993a). In unclear cases, three-dimensional (3-D) sonography, magnetic resonance (MR) imaging, or diagnostic laparoscopy can help clariy anatomy (Parker, 2012; Tanaka, 2014). Laparoscopically, an enlarged protuberance is found lying outside the round ligament and coexistent with a normal distal fallopian tube and ovary.
FIGURE 19-7 Interstitial ectopic pregnancy. A.This parasagittal view using transvaginal sonography shows an empty uterine cavity and a mass that is cephalad and lateral to the uterine fundus (calipers). B. Intraoperative photograph during laparotomy and before cornual resection of the same ectopic pregnancy. In this frontal view, the bulging right-sided interstitial ectopic pregnancy is lateral to the round ligament insertion and medial to the isthmic portion of the fallopian tube. (Used with permission from Drs. David Rogers and Elaine Duryea.)