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Ectopic pregnancy occurs when a conceptus is implanted outside of the uterine cavity.

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Epidemiology

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Reported pregnancies include live births, legally induced abortions, and ectopic pregnancies. The current incidence of ectopic pregnancy is difficult to determine from available data but is probably increasing. Overestimation of ectopic pregnancy incidence is possible because the denominator, reported pregnancies, could be biased by lack of reporting of illegally terminated pregnancies or undetected spontaneous abortions. Reasons postulated for the increased incidence of ectopic pregnancy include the increased incidence of sexually transmitted tubal infections, unsuccessful tubal sterilizations, assisted reproductive techniques, previous pelvic surgery, and more sensitive and earlier diagnostic techniques.

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The case fatality rate per 10,000 ectopic pregnancies decreased from 35.5 in 1970 to 8.8 in 1980 to 3.8 in 1989. However, nonwhite women overall have a 3.4 times greater risk of death than white women. Teenagers as a group have the highest mortality rate. The observed decreased mortality is attributed largely to improved diagnostics and also a heightened awareness among medical personnel. However, ectopic pregnancy remains the leading cause of maternal death in the first trimester of pregnancy and is the second leading cause of maternal mortality overall.1

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Pathophysiology

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Fertilization of the oocyte usually occurs in the ampullary segment of the fallopian tube. In normal pregnancy, after fertilization, the zygote passes along the fallopian tube and implants into the endometrium of the uterus. An ectopic pregnancy occurs when the zygote implants in any location other than the uterus. The vast majority of ectopic pregnancies occur in the fallopian tube. Extratubal sites include the abdominal cavity, cervix, and ovary. Abdominal ectopic pregnancies most commonly derive from early rupture or abortion of a tubal pregnancy, with subsequent reimplantation in the peritoneal cavity.

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A normal placenta is uncommon in ectopic pregnancies, possibly accounting for the much higher incidence of a blighted ovum in ectopic pregnancy. Tubal abortion occurs when the vascular supply to the placenta is disrupted, with bleeding into the fallopian tube and hematoma formation. Intermittent distention of the fallopian tube with blood can occur, with leakage of blood from the fimbriated end of the fallopian tube into the peritoneal cavity. The aborting ectopic pregnancy and associated hematoma can be completely or partially extruded out of the end of the fallopian tube or through a rupture site in the tubal wall. Tubal rupture is usually spontaneous; however, in anecdotal accounts, precipitating factors include trauma associated with coitus or a bimanual examination.

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Conditions causing damage to the fallopian tube pose the highest risk for subsequent ectopic pregnancy.2 Major risk factors are shown in Table 101-1. Pregnancy in a patient with prior tubal surgery for sterilization is assumed to be an ectopic pregnancy until proven otherwise. An analysis of 94,118 pregnancies conceived using assisted reproductive technologies found that 2009 (2.1%) were ectopic.3 However, >50% of cases of ectopic pregnancy occur ...

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