Use of double decidual sac sign to confirm intrauterine pregnancy location prior to sonographic visualization of embryonic contents

Objectives To determine the diagnostic accuracy of the double decidual sac sign (DDSS) for predicting an intrauterine pregnancy (IUP) prior to visualization of embryonic contents, using modern high-resolution transvaginal sonography (TVS). Methods The study was conducted following STARD guidelines and participants were recruited prospectively from Nurture Fertility, Nottingham, UK, following in-vitro fertilization/intracytoplasmic sperm injection treatment between 1 January 2015 and 31 October 2015. Women were excluded if there was no evidence of intrauterine fluid collection during the index test, a yolk sac or fetal pole was visible during the index test, no outcome data were available or pregnancy location could not be determined by the reference standard. The index test consisted of TVS at 32–34 days' gestation using a high-frequency transvaginal probe. Reference standard was TVS at 7 weeks' gestation. The outcome of interest was an IUP. Results A total of 67 intrauterine fluid collections were observed and included in the analysis, of which 61 exhibited the DDSS and 65 were proven to be IUPs. Two ectopic pregnancies were included, neither of which demonstrated the DDSS. The DDSS therefore had a sensitivity of 93.9% (95% CI, 85.0–98.3%), specificity of 100% (95% CI, 15.8–100%) and overall diagnostic accuracy of 94.0% (95% CI, 88.3–99.7%) for predicting an IUP. The negative likelihood ratio and positive and negative predictive values were 0.06 (95% CI, 0.02–0.16), 100% (95% CI, 94.1–100%) and 33.3% (95% CI, 4.3–77.7%), respectively. Conclusion With modern high-resolution TVS, presence of the DDSS can be used to confirm accurately IUP location prior to sonographic visualization of embryonic contents, and therefore to exclude effectively ectopic pregnancy. Absence of the DDSS, however, does not preclude an IUP. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.