Pregnancy of unknown location

The term pregnancy of unknown location (PUL) is assigned when neither an intrauterine pregnancy (IUP) or an ectopic pregnancy is identified on transvaginal ultrasound in the context of a positive pregnancy test.

Clinical presentation

• pelvic pain

• vaginal bleeding

• positive pregnancy test

Pathology

Markers

• serial beta-hCG: has an adjunct role in the diagnosis of ectopic pregnancy, and is useful in the follow-up of clinically stable patients 

• serum progesterone: lack of progesterone has been considered an indication of non-viability ³

  • <5 ng/mL is a good indicator of non-viability, however, larger values cannot exclude an ectopic pregnancy ⁴

Radiographic features

These patients will present with a "normal" pelvic ultrasound, with no signs of an intrauterine pregnancy and a normal adnexa ⁵.

In some cases, an endometrial fluid collection can be noted, which can be differentiated from early pregnancy by the absence of a double decidual sign.

Treatment and prognosis 

Since the most likely underlying diagnosis is non-viable intrauterine pregnancy ⁶, methotrexate and/or surgical intervention is not recommended in a hemodynamically stable patient ⁶. Instead, a short interval repeat ultrasound examination and quantitative beta-hCG level are generally appropriate ^5,6.

While patients and referring doctors may want conclusive answers, it is important to safeguard both mother and child by delivering accurate and appropriate conclusions that lead to intervention, mostly in instances of absolutely failed intrauterine pregnancy or visible ectopic pregnancy ⁸.

Intervening in women with a "pregnancy of unknown location" (since only a small fraction of these may be hidden ectopic pregnancies) can be far more detrimental than monitoring serial beta-hCG levels and repeating ultrasound scans at suitable intervals ⁸.

Differential diagnosis

A pregnancy of unknown location reflects four possibilities:

• very early pregnancy not yet detected with ultrasound

• non-viable intrauterine pregnancy not detected with ultrasound

• complete miscarriage

• unidentified ectopic pregnancy

See also

• ectopic pregnancy

• early pregnancy

• pregnancy of uncertain viability