Which ultrasound features definitively diagnose an intra-uterine pregnancy in the first trimester?
Searches
We will search the following electronic bibliographic databases: Cochrane Central Register of Controlled Trials (CENTRAL), Database of Abstracts of Reviews of Effects (DARE), Medical Literature Analysis and Retrieval System Online (MEDLINE) and Embase. The search strategy will include only terms relating to or describing the intervention. The search strategy for MEDLINE will be available in the published protocol. The search will be limited to articles published in English. Studies published between 1946 and the date the searches are run will be sought. The searches will be re-run just before the final analysis and further studies retrieved for inclusion. We will also visually scan reference lists from relevant studies in an attempt to locate additional studies that may not have been identified by searching the electronic databases.
Types of study to be included
We will include randomised controlled trials and cohort studies that report original data regarding the ultrasound diagnosis of an early intrauterine pregnancy. Case reports and case studies where the sample size is <10 will be excluded due to the high risk of bias. Commentaries, narrative reviews and letters will also be excluded.
Condition or domain being studied
Ultrasound diagnosis of early intrauterine pregnancy
Participants/ population
Inclusion criteria: pregnant women <12/40, singleton pregnancies,trans-vaginal or transabdominal ultrasound examination
Exclusion criteria: non-pregnant women, pregnant women >12/40, multiple pregnancies, pregnancies later confirmed to have chromosomal or structural abnormalities
Intervention(s), exposure(s)
Multiple ultrasound features have been proposed as being diagnostic of an intrauterine pregnancy with varying reported specificities and sensitivities. These include: a decidual reaction, gestation sac, double decidual sac sign, intradecidual sign, amniotic rim sign, yolk sac and fetal pole.
Comparator(s)/ control
N/A
Context
Studies in infertility and early pregnancy departments will be included
Outcome(s)
Primary outcomes
Accurate diagnosis of an intrauterine pregnancy
Secondary outcomes
Accurate diagnosis/exclusion of an extra-uterine pregnancy
Data extraction, (selection and coding)
Two independent reviewers (AR and SD) will screen the retrieved titles and abstracts selecting and excluding those that clearly do not meet the eligibility criteria; disagreements between reviewers will be resolved by consensus or a third party (NRF). One author (AR) will obtain full articles of all potentially relevant studies, which will be examined for eligibility independently by two reviewers (AR andSD) Rejected citations will be justified. Disagreements between the reviewers will again be resolved by consensus, or when not possible, by consulting a third author (NRF).
Two review authors (AR and SD) will extract the data independently from included studies using a standardized data extraction form designed and pilot-tested by the authors. The following data will be extracted from the included studies: study characteristics (design, setting, aims, time period, population, inclusion and exclusion criteria); study methodology; details of the intervention i.e. ultrasound feature under evaluation; pregnancy outcome if reported; quality and accuracy of results and information for assessing the risk of bias.
If there are data queries the corresponding author of the study will be contacted. If this is not possible, or generates no response after 4 weeks, the study will be excluded and listed as ‘a potentially relevant study’.
The names of article authors and titles of the included studies will be juxtaposed to identify duplicate publications; in case of duplicates both articles will be considered as a unique study.
Risk of bias (quality) assessment
We will minimize the potential impact of publication and reporting bias by performing a comprehensive search for eligible studies and by looking for duplication of data. Each study identified will be analyzed by two review authors (AR and SD) independently using the Newcastle-Ottawa scale (Wells et al.) Disagreements between the review authors over the risk of bias in particular studies will be resolved by discussion, with involvement of a third review author (NRF) where necessary.
Strategy for data synthesis
Accuracy measures including sensitivity and specificity and likelihood ratios for abnormal and normal test results will be calculated for each study, separately for each test threshold.
Heterogeneity will be assessed graphically using forest plots and statistically using chi-squared test to aid in decisions regarding how to proceed with quantitative synthesis.
Where studies have used the same intervention and outcome measure, we will pool the results using a random-effects meta-analysis
If a quantitative approach is not appropriate due to significant clinical heterogeneity, we will refrain from pooling and describe the results narratively and report the accuracy measures within each study.
All statistical analyses will be performed using the SPSS statistical package.
Analysis of subgroups or subsets
Subgroup analyses will be attempted for each ultrasound feature identified, for example a decidual reaction, gestation sac, double decidual sac sign, intradecidual sign, amniotic rim sign, yolk sac and fetal pole.
Dissemination plans
A paper will be submitted to a leading journal in this field. Furthermore, should the findings of the review warrant a change in practice, a one page summary report will be prepared and sent to lead clinicians and healthcare professionals in the NHS.
Contact details for further information
Alison Richardson
Nurture Fertility, Division of Obstetrics & Gynaecology, School of Clinical Sciences, University of Nottingham, Nottingham, NG7 2UH, United Kingdom
allyrichardson@hotmail.co.uk
Organisational affiliation of the review
Nurture Fertility, Division of Obstetrics & Gynaecology, School of Clinical Sciences, University of Nottingham, Nottingham, NG7 2UH, United Kingdom
Review team
Dr Alison Richardson, Nurture Fertility, Division of Obstetrics & Gynaecology, School of Clinical Sciences, University of Nottingham, Nottingham, NG7 2UH, United Kingdom Mr Nick Raine-Fenning, Nurture Fertility, Division of Obstetrics & Gynaecology, School of Clinical Sciences, University of Nottingham, Nottingham, NG7 2UH, United Kingdom Dr Sam Dobson, Department of Obstetrics and Gynaecology, Queen’s Medical Centre, Derby Road, Nottingham, NG7 2UH, United Kingdom
Formal screening of search results against eligibility criteria
Data extraction
Risk of bias (quality) assessment
Data analysis
Prospective meta-analysis
PROSPERO This information has been provided by the named contact for this review. CRD has accepted this information in good faith and registered the review in PROSPERO. CRD bears no responsibility or liability for the content of this registration record, any associated files or external websites.
