Are Abnormal Yolk Sac Characteristics Important Factors in Abortion Rates?

Background: This study was undertaken to determine if there were different abortion rates between normal and abnormal yolk sacs. Materials and Methods: In this cohort study, the yolk sac characteristics of 193 consecutive pregnant women, of 5-6.5 weeks gestation, with normal body mass index (BMI) were prospectively evaluated. All patients underwent two-dimensional transvaginal ultrasonography, which was performed by the same sonographer. We considered the following yolk sac characteristics as normal for classification: diameter: 2-5 mm; round shape; absence of degenerative changes; equal number with embryos; echogenic rim and hypoechoic center. Yolk sacs that had diameters smaller than 2 mm or larger than 5 mm; a shape that was not round (i.e., oval or distorted); the presence of degenerative changes; hyper- or hypo-echogenic rim; hyperechoic center and unequal number with embryos were considered abnormal. Based on the above classification, patients were divided into two groups, study (abnormal yolk sac) and control (normal yolk sac). The study group contained 22 cases and the control group consisted of 164 cases. The primary outcome measure was the abortion rate between both groups. Chi-square and students’t test were used for data analysis. Results: A total of 193 cases were evaluated. We excluded 2 cases. Among the remaining 191 cases, 22 (11.51%) had abnormal yolk sacs of which spontaneous abortion occurred in 14 (63.63%) cases. In the control group, out of 169 (89.49%) cases, spontaneous abortion was noted in 6 (3.55%). There was a statistically significant difference in abortion rates between the two groups (p=0.000). Conclusion: According to the results of this study, it is obvious that abnormal yolk sac characteristics are associated with spontaneous abortion.