Association between three-dimensional transvaginal sonographic markers and outcome of pregnancy of unknown location: a pilot study.

OBJECTIVE: To assess the accuracy of three-dimensional (3D) transvaginal sonographic (TVS) parameters in predicting the evolution of a pregnancy of unknown location (PUL).

METHODS: This was a prospective observational study performed at the early pregnancy unit of a university hospital from September 2008 to June 2012. Women with a positive pregnancy test without any signs of intra- or extrauterine pregnancy at their first TVS examination were considered eligible and a 3D dataset containing the entire uterus was acquired. An experienced observer analyzed all 3D datasets for assessment of the following parameters: endometrial thickness, volume, mean gray-scale index and asymmetry. Women were followed until they were classified as having: (i) non-visualized pregnancy loss (NVPL); (ii) intrauterine pregnancy (IUP); or (iii) ectopic pregnancy or persistent PUL. We compared the values of the TVS parameters across the three groups. We also assessed the area under the receiver-operating characteristics curve of the 3D-TVS parameters in comparison to that for serum β-human chorionic gonadotropin (β-hCG) ratio (48 h/baseline) to predict PUL outcome. We then evaluated whether combining the 3D-TVS parameters with serum β-hCG ratio improved the predictive accuracy for PUL outcome by performing a logistic regression analysis.

RESULTS: During the study period 4939 consecutive pregnant women presented at the unit for their initial TVS examination and 325 (7%) were classified as having a PUL, of whom 161 women were enrolled and had a 3D scan of the uterus. However, 19 were excluded because of incomplete follow-up. Data from 142 women with PUL were therefore included in the analysis and the outcomes of these women were: NVPL in 98 (69%), IUP in 27 (19%) and ectopic pregnancy + persistent PUL in 14 + 3 = 17 (12%). Endometrial thickness, endometrial volume and the proportion of women with asymmetric endometrial shape differed significantly between the outcome groups. Endometrial thickness and volume could be used as reasonable predictors of both NVPL and IUP, whereas asymmetric endometrial shape and mean gray-scale index could be used as reasonable predictors of IUP only. The best single parameter to predict PUL outcomes was the β-hCG ratio. Regression analysis demonstrated that endometrial volume and endometrial shape asymmetry added significantly to the β-hCG ratio in predicting IUP but not NVPL.

CONCLUSIONS: 3D-TVS markers have a low diagnostic accuracy in predicting PUL outcome. The addition of endometrial volume and shape asymmetry improves the accuracy of the β-hCG ratio in predicting IUP. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.