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Following fertilization and fallopian tube transit, the blastocyst normally implants in the endometrial lining of the uterine cavity. Implantation elsewhere is considered ectopic. In the United States, numbers from an insurance database and from Medicaid claims showed ectopic pregnancy rates of 1.54 percent and 1.38 percent, respectively, in 2013 (Tao, 2017). Ectopic implantation accounts for 3 percent of all pregnancy-related deaths (Creanga, 2017). Fortunately, beta-human chorionic gonadotropin (β-hCG) assays and transvaginal sonography (TVS) aid earlier diagnosis, maternal survival, and fertility conservation.
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Of ectopic pregnancies, nearly 95 percent implant in the fallopian tube’s various segments (Fig. 2-13, p. 26). The ampulla (70 percent) is the most frequent site (Fig. 12-1). The rate for isthmic implantation is 12 percent; fimbrial, 11 percent; and interstitial, 2 percent (Bouyer, 2002). Nontubal ectopic pregnancies compose the remaining 5 percent and implant in the ovary, peritoneal cavity, cervix, or prior cesarean scar. Occasionally, a multifetal pregnancy contains one conceptus with normal uterine implantation and the other implanted ectopically. This is termed a heterotopic pregnancy (p. 231).
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For all ectopic pregnancy sites, management is influenced by pregnancy viability, gestational age, maternal health, desires for the index pregnancy and for future fertility, physician skill, and available resources. Regardless of location, D-negative women with an ectopic pregnancy are given anti-D immunoglobulin. In first-trimester pregnancies, a single intramuscular 50- or 120-μg dose is appropriate. Later gestations are given 300 μg (American College of Obstetricians and Gynecologists, 2019b).
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Abnormal fallopian tube anatomy underlies most cases of tubal ectopic pregnancy. Surgeries for a prior tubal pregnancy, for fertility restoration, or for sterilization confer the highest risk. After one prior ectopic pregnancy, the chance of another nears 10 percent (de Bennetot, 2012). Previous tubal infection, which can distort normal tubal anatomy, is another risk. Specifically, one episode of salpingitis can be followed by a subsequent ectopic pregnancy in up to 9 percent of women (Westrom, 1992). Peritubal adhesions that form from salpingitis, appendicitis, or endometriosis also raise chances.
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Infertility and the use of assisted reproductive technologies (ART) to overcome it are linked to increased ectopic pregnancy rates (Li, 2015; Perkins, 2015). Newer techniques aim to lower this rate with ART (Londra, 2015; Zhang, 2017). Smoking is another known association, although the underlying mechanism is unclear (Hyland, 2015). Last, with any form of contraception, the absolute number of ectopic pregnancies declines because pregnancy is effectively prevented. However, some methods more efficiently prevent intracavity implantation and with their failure, ectopic implantation is favored. These methods are tubal ...