Pregnancy of unknown location
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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.
positive pregnancy test
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
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.
A pregnancy of unknown location reflects four possibilities:
very early pregnancy not yet detected with ultrasound
non-viable intrauterine pregnancy not detected with ultrasound
unidentified ectopic pregnancy
- 1. Banerjee S, Aslam N, Zosmer N et-al. The expectant management of women with early pregnancy of unknown location. Ultrasound Obstet Gynecol. 1999;14 (4): 231-6. doi:10.1046/j.1469-0705.1999.14040231.x - Pubmed citation
- 2. Banerjee S, Aslam N, Woelfer B et-al. Expectant management of early pregnancies of unknown location: a prospective evaluation of methods to predict spontaneous resolution of pregnancy. BJOG. 2001;108 (2): 158-63. BJOG (link) - Pubmed citation
- 3. Boyraz G, Bozdağ G. Pregnancy of unknown location. J Turk Ger Gynecol Assoc. 2013;14 (2): 104-8. doi:10.5152/jtgga.2013.74317 - Free text at pubmed - Pubmed citation
- 4. Mol BW, Lijmer JG, Ankum WM et-al. The accuracy of single serum progesterone measurement in the diagnosis of ectopic pregnancy: a meta-analysis. Hum. Reprod. 1999;13 (11): 3220-7. Pubmed citation
- 5. Rodgers SK, Chang C, DeBardeleben JT, Horrow MM. Normal and Abnormal US Findings in Early First-Trimester Pregnancy: Review of the Society of Radiologists in Ultrasound 2012 Consensus Panel Recommendations. Radiographics : a review publication of the Radiological Society of North America, Inc. 35 (7): 2135-48. doi:10.1148/rg.2015150092 - Pubmed
- 6. Doubilet PM, Benson CB, Bourne T, Blaivas M. Diagnostic Criteria for Nonviable Pregnancy Early in the First Trimester. N. Engl. J. Med. 2013, 369 (15), 1443-1451. PubMed
- 7. https://obgyn.onlinelibrary.wiley.com/doi/pdf/10.1576/toag.10.4.224.27438 - to be linked
- 8. Shuchi K. Rodgers, Crystal Chang, John T. DeBardeleben, Mindy M. Horrow. Normal and Abnormal US Findings in Early First-Trimester Pregnancy: Review of the Society of Radiologists in Ultrasound 2012 Consensus Panel Recommendations. (2015) RadioGraphics. doi:10.1148/rg.2015150092