Ectopic pregnancy is the implantation of a fertilized ovum outside of the endometrial cavity. The incidence of ectopic pregnancy plateaued in the early 1990s at approximately 19 per 1,000 pregnancies, by the most recent estimates from the Centers for Disease Control and Prevention. The death rate from ectopic pregnancy has declined by approximately 90% since 1979 likely due to earlier detection. The cause of ectopic implantation of the zygote is hypothesized to be delayed transit of the zygote secondary to abnormal fallopian tubes, which may have abnormal angulation or adhesions from inflammation or previous surgery. Risk factors include previous pelvic surgery, history of pelvic inflammatory disease, previous ectopic pregnancy, diethylstilbestrol (DES) exposure, prior tubal ligation, ovulation induction, in vitro fertilization, and intrauterine device. In most ectopic pregnancies, rupture occurs at or before the eighth week of gestation. Rupture in cornual (interstitial) pregnancies and abdominal pregnancies can occur later (8-10 weeks), often with life-threatening hemorrhage.

The classic presentation, seen in less than 50% of patients, consists of (1) abnormal vaginal bleeding (75%), (2) pelvic pain, and (3) palpable adnexal mass in the setting of a positive Β-human chorionic gonadotropin (Β-hCG). Other clinical signs include secondary amenorrhea, a positive Β-hCG that does not rise greater than 66% in 48 hours (with intrauterine pregnancy [IUP], levels roughly double every 48 hours), and falling hematocrit or shock.

Initial evaluation for suspected ectopic pregnancy (vaginal bleeding with or without pelvic pain) in a patient with a positive Β-hCG.

Transabdominal scan with full bladder, then endovaginal examination after bladder is emptied. A Foley catheter may be placed to facilitate adequate bladder filling.

The main question to be answered is whether an IUP is present. Some normal sonographic “milestones” are given in Table 43-1. The following is a list of
the possible sonographic appearances and the meaning of each, given a positive Β-hCG (unless otherwise indicated, all mean sac diameters in the subsequent text refer to the endovaginal examination):