Endometrial thickness predicts intrauterine pregnancy in patients with pregnancy of unknown location

Objective: To determine whether endometrial thickness and other parameters are useful predictors of normal intrauterine pregnancy (IUP) in the setting of vaginal bleeding and sonographic diagnosis of pregnancy of unknown location (PUL). Methods: We reviewed the clinical and sonographic records of all 591 patients with vaginal bleeding and a sonographic diagnosis of PUL between 1 July 2005 and 30 June 2006. Data on maternal age, gravidity, parity, estimated gestational age by last menstrual period (EGA by LMP), endometrial thickness and serum β-human chorionic gonadotropin (β-hCG) were collected. Complete data were available for 517 patients, 40 (7.7%) of whom ultimately had normal IUPs. A logistic regression model was constructed using a stepwise procedure to identify variables significantly associated with the outcome of normal IUP. The validity of the model was assessed by receiver-operating characteristics (ROC) curve and Hosmer-Lemeshow Chi-square analysis. Results: Four variables (maternal age, EGA by LMP, endometrial thickness and serum β-hCG) were significant in the prediction of normal IUP (area under the ROC curve = 0.86). As maternal age, EGA by LMP and β-hCG increased, the likelihood of a normal IUP decreased, while as the endometrial thickness increased, the likelihood of a normal IUP increased. For each millimeter increase in endometrial thickness, the odds increased by 27% that the patient would have a normal IUP. No normal IUP had an endometrial thickness <8 mm. Conclusion: Increased endometrial thickness predicts normal IUP in patients who present with vaginal bleeding and PUL.