OC38.02: Screening for Down syndrome with a twostep approach using firsttrimester combined screening followed by secondtrimester ultrasound examination: an interventional study

Objective: To identify ultrasound measurements which are the best predictors of the presence of retained products of conception (RPOC) within the uterine cavity in women with clinical suspicion of incomplete miscarriage. Methods: This was a prospective study of 200 women with a diagnosis of incomplete miscarriage who were referred for surgical evacuation. All women had a positive urine pregnancy test, and ultrasound findings suggestive of RPOC. The indication for intervention was heavy vaginal bleeding or continuous symptoms following ≥7 days of expectant management. The endometrial thickness and the volume of RPOC (D1 × D2 × D3 × 0.532) were measured preoperatively. The final diagnosis of incomplete miscarriage was based on histopathologic evidence of chorionic villi in the surgical specimen. Results: 189 (94.5%) women had evidence of chorionic villi on histology whilst decidua was only found in the remaining 11 (5.5%) women. On multiple logistic regression analysis the best discriminator between RPOC and decidua was endometrial volume, whilst the endometrial thickness was not statistically significant. Using a cut off level ≥1 ml the odds of tissue representing chorionic villi were 137 (95% CI 24 to 778). Conclusion: The measurement of endometrial volume on ultrasound scan is a better test to diagnose incomplete miscarriage than endometrial thickness.