Following fertilization and fallopian tube transit, the blastocyst normally implants in the endometrial lining of the uterine cavity. Implantation elsewhere is considered ectopic and comprises 1 to 2 percent of all first-trimester pregnancies in the United States. This small proportion disparately accounts for 6 percent of all pregnancy-related deaths (Berg, 2010; Stulberg, 2013). In addition, the chance for a subsequent successful pregnancy is reduced after an ectopic pregnancy. Fortunately, urine and serum beta-human chorionic gonadotropin (β-hCG) assays and transvaginal sonography have made earlier diagnosis possible. And as a result, both maternal survival rates and conservation of reproductive capacity are improved.
Nearly 95 percent of ectopic pregnancies are implanted in the various segments of the fallopian tube and give rise to fimbrial, ampullary, isthmic, or interstitial tubal pregnancies (Fig. 19-1). As shown, the ampulla is the most frequent site, followed by the isthmus. The remaining 5 percent of nontubal ectopic pregnancies implant in the ovary, peritoneal cavity, cervix, or prior cesarean scar. Occasionally, a multifetal pregnancy is composed of one conceptus with normal uterine implantation coexisting with one implanted ectopically. The natural incidence of these heterotopic pregnancies approximates 1 per 30,000 pregnancies. However, because of assisted reproductive technologies (ART), their incidence has increased to 1 in 7000 overall, and following ovulation induction, it may be as high as 0.5 to 1 percent (Mukul, 2007). Rarely, twin tubal pregnancy with both embryos in the same tube or with one in each tube has been reported (Eze, 2012; Svirsky, 2010).
Sites of implantation of 1800 ectopic pregnancies from a 10-year population-based study. (Data from Callen, 2000; Bouyer, 2003.)
Regardless of location, D-negative women with an ectopic pregnancy who are not sensitized to D-antigen should be given IgG anti-D immunoglobulin (American College of Obstetricians and Gynecologists, 2013). In first-trimester pregnancies, a 50-μg or a 300-μg dose is appropriate, whereas a standard 300-μg dose is used for later gestations.
Abnormal fallopian tube anatomy underlies many cases of tubal ectopic pregnancy. Surgeries for a prior tubal pregnancy, for fertility restoration, or for sterilization confer the highest risk of tubal implantation. After one previous ectopic pregnancy, the chance of another approximates 10 percent (Ankum, 1996; Skjeldestad, 1998). Prior sexually transmitted disease or other tubal infection, which can distort normal tubal anatomy, is another common risk factor. Specifically, one episode of salpingitis can be followed by a subsequent ectopic pregnancy in up to 9 percent of women (Westrom, 1992). Similarly, peritubal adhesions subsequent to salpingitis, appendicitis, or endometriosis may increase the risk for tubal pregnancy. Salpingitis isthmica nodosa, which is a condition in which epithelium-lined diverticula extend into a ...