Diagnostic criteria for retained products of conception—A scoping review

INTRODUCTION: Numerous studies have been performed assessing optimal treatment regimens for evacuating (retained) products of conception from the uterus, but standardized criteria for diagnosing retained products of conception (RPOC) are still lacking. We aim to provide an overview of diagnostic criteria in current literature, used to diagnose RPOC after induced first‐trimester abortion or early pregnancy loss. MATERIAL AND METHODS: Pubmed, EMBASE, and the Cochrane library were searched systematically up until March 2020 for English articles reporting on induced abortion or early pregnancy loss. Articles not specifying diagnostic criteria used to assess completeness of treatment were excluded, as were conference abstracts, expert opinions, reviews, and case reports. Four elements of diagnostic criteria were described: diagnostic tools, parameters used within these tools, applied cut‐off values, and timing of follow up. Additionally, a meta‐analysis was performed assessing diagnostic qualities of the most often applied diagnostic tool and parameter. RESULTS: The search strategy yielded 1233 unique articles, of which 248 were included, with a total of 339 517 participants. In the 79 included randomized controlled trials, six diagnostic tools to assess RPOC were identified, combined in 14 ways, with 55 different cut‐off values. In 169 observational studies, seven diagnostic tools were identified, used in 28 combinations, applying 89 different cut‐off values. Transvaginal ultrasonographic measurement of endometrial thickness with a cut‐off value of at least 15 mm indicating RPOC, was used most frequently. In the timing of follow‐up there was great variation, with 55 and 107 different combinations in randomized controlled trials and observational studies, respectively. Assessment of treatment success was scheduled most often around 2 weeks after treatment. Diagnostic qualities of endometrial thickness of 15 mm or more was not adequately assessed. CONCLUSIONS: There is wide variation in the way RPOC are assessed, and the criteria used to define RPOC following induced abortion and early pregnancy loss; ultrasonographic measurement of endometrial thickness, with a cut‐off of 15 mm or more 2 weeks after primary treatment is the most widely used diagnostic approach. A meta‐analysis on diagnostic accuracy of endometrial thickness of 15 mm or more did not lead to solid results. These findings can be a first step to develop a workable standard of establishing RPOC after induced abortion or early pregnancy loss.