Accuracy of first-trimester ultrasound in diagnosis of intrauterine pregnancy prior to visualization of the yolk sac: a systematic review and meta-analysis.
OBJECTIVE
To evaluate the diagnostic accuracy of ultrasound in predicting the location of an intrauterine pregnancy before visualization of the yolk sac is possible.


METHODS
This was a systematic review conducted in accordance with the PRISMA statement and registered with PROSPERO. We searched MEDLINE, EMBASE and The Cochrane Library for relevant citations. Studies were selected in a two-stage process and their data extracted by two reviewers. Accuracy measures were calculated for each ultrasound sign, i.e. gestational sac, double decidual sac sign, intradecidual sign, chorionic rim sign and yolk sac. Individual study estimates were plotted in summary receiver-operating characteristics curves and forest plots for examination of heterogeneity. The quality of included studies was assessed.


RESULTS
Seventeen studies including 2564 women were selected from 19 959 potential papers. Following meta-analysis, the presence of a gestational sac on ultrasound examination was found to predict an intrauterine pregnancy with a sensitivity of 52.8% (95% CI, 38.2-66.9%) and specificity of 97.6% (95% CI, 94.3-99.0%). The corresponding performance of the double decidual sac sign, intradecidual sign, chorionic rim sign and yolk sac were: 81.8% (95% CI, 68.1-90.4%) and 97.3% (95% CI, 76.1-99.8%); 66.1% (95% CI, 58.9-72.8%) and 100% (95% CI, 91.0-100%); 79.9% (95% CI, 73.0-85.7%) and 97.1% (95% CI, 89.9-99.6%); and 42.2% (95% CI, 27.7-57.9%) and 100% (95% CI, 54.1-100%), respectively.


CONCLUSIONS
Visualization of a gestational sac, double decidual sac sign, intradecidual sign or chorionic rim sign increases the probability of an intrauterine pregnancy but is not as accurate for diagnosis as the detection of the yolk sac. However, the findings were limited by the small number and poor quality of the studies included and heterogeneity in the index test and reference standard.
Nurture Fertility, The East Midlands Fertility Clinic, Nottingham, UK.|Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, UK.
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Richardson
School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
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I
Gallos
Nottingham University Hospitals NHS Trust, Queen's Medical Centre, Nottingham, UK.
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Dobson
Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, UK.
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BK
Campbell
School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
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Coomarasamy
Nurture Fertility, The East Midlands Fertility Clinic, Nottingham, UK.|Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, UK.
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Raine-Fenning
D003656:Decidua / Q000000981:diagnostic imaging; D005260:Female; D058746:Gestational Sac / Q000000981:diagnostic imaging*; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011271:Pregnancy, Ectopic / Q000000981:diagnostic imaging / Q000517:prevention & control; D016216:Ultrasonography, Prenatal / Q000379:methods*; D015017:Yolk Sac / Q000000981:diagnostic imaging*
QUADAS-2; diagnostic accuracy; intrauterine; pregnancy; systematic review; ultrasound