Clinical Review

Pregnancy of unknown location: Evidence-based evaluation and management

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Identifying pregnancy of unknown location early with a combination of screening modalities guides management of intrauterine or ectopic pregnancy


 

References

CASE Woman with bleeding in early pregnancy

A 31-year-old woman (G1P0) presents to the local emergency department (ED) due to bleeding in pregnancy. She reports a prior open appendectomy for ruptured appendix; she denies a history of sexually transmitted infections, smoking, and contraception use. She reports having regular menstrual cycles and trying to conceive with her husband for 18 months without success until now.

The patient reports that the previous week she took a home pregnancy test that was positive; she endorses having dark brown spotting for the past 2 days but denies pain. Based on the date of her last menstrual period, gestational age is estimated to be 5 weeks and 1 day. Her human chorionic gonadotropin (hCG) level is 1,670 mIU/mL. Transvaginal ultrasonography demonstrates a normal uterus with an endometrial thickness of 10 mm, no evidence of an intrauterine pregnancy (IUP), normal adnexa bilaterally, and scant free fluid in the pelvis.

Identifying and evaluating pregnancy of unknown location

A pregnancy of unknown location (PUL) is defined by a positive serum hCG level in the absence of a visualized IUP or ectopic pregnancy (EP) by pelvic ultrasonography.

Because of variations in screening tools and clinical practices between institutions and care settings (for example, EDs versus specialized outpatient offices), the incidence of PUL is difficult to capture. In specialized early pregnancy clinics, the rate is 8% to 10%, whereas in the ED setting, the PUL rate has been reported to be as high as 42%.1-6 While approximately 98% to 99% of all pregnancies are intrauterine, only 30% of PULs will continue to develop as viable ongoing intrauterine gestations.7-9 The remainder are revealed as failing IUPs or EPs. To counsel patients, set expectations, and triage to appropriate management, it is critical to diagnose pregnancy location as efficiently as possible.

Ectopic pregnancy

Ectopic pregnancies represent only 1% to 2% of conceptions (both spontaneous and through assisted reproduction) and occur most commonly in the fallopian tube, although EPs also can implant in the cornua of the uterus, the cervix, cesarean scar, and more rarely on the ovary or abdominal viscera.10,11 Least common, heterotopic pregnancies—in which an IUP coexists with an EP—occur in 1 in 4,000 to 30,000 pregnancies, more commonly in women who used assisted reproduction.11

Major risk factors for EP include a history of tubal surgery, sexually transmitted infections (particularly Chlamydia trachomatis), pelvic inflammatory disease, conception with an intrauterine device in situ, and a history of prior EP or tubal surgery, particularly prior tubal ligation; minor risk factors include a history of infertility (excluding known tubal factor infertility) or smoking (in a dose-dependent manner).11,12 The concern for an EP is heightened in patients with these risk factors.

Because of the possibility of rupture and life-threatening hemorrhage, EP carries a risk of significant morbidity and mortality.13 Ruptured EPs account for approximately 2.7% of all maternal deaths each year.14 When diagnosed sufficiently early in a stable patient, most EPs can be managed medically with methotrexate, a folic acid antagonist.15 Ectopic pregnancies also may be managed surgically, and emergency surgery is indicated in women with evidence of EP rupture and intraperitoneal bleeding.

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