Yolk Sac and Embryonic Heart Rate as Predictors for Early Pregnancy Loss

Objectives The aim of our study was to investigate the embryonic heart rate and the yolk sac features during the first trimester and their predictive value regarding first trimester pregnancy loss. Methods We examined the yolk sac features: dimensions, shape, vascularization rate and the embryonic heart rate in 126 pregnancies between 5 and 10 weeks of gestational age; 17 of them were ended by a miscarriage. Results The visualizing rate of the yolk sac in miscarriages after the embryo had been formed was significantly higher in those women who demonstrated fetal heart activity (80,4%) than in those who did not (51,5%). A diameter of the yolk sac above 6 mm was observed in 2 of 109 normal pregnancies (1,8%) and in 4 of 17 spontaneous abortions (23,5%). A diameter above 8 mm was seen in only one of the cases with normal development (0,9%), but it was seen in 3 of the pathological courses (17,6%). In normal pregnancies with embryonic heartbeats, a deformed or an absent yolk sac was never detected. The cases that ended with spontaneous abortion were marked by a significant lower embryonic heart rate, a smaller or absent yolk sac, an irregular-shaped or a large yolk sac. The visualization rate for yolk sac vessels was 78,3%. The highest visualization rates were obtained in the 7th and 8th weeks of gestation reaching values of 89,2%. In the cases ended with spontaneous abortion the doppler examination showed a poor vascularization of the yolk sac. Conclusions The embryonic heart rate and the yolk sac dimensions progressively increase in healthy pregnancies during the first trimester. Embryonic bradycardia, the absence or an abnormal yolk sac, are predictors of poor pregnancy outcome during the first 12 weeks.