The embryonal yolk sac in disordered early pregnancy

Abstract

The detection rate and size of the yolk sac were evaluated by means of vaginal sonography in a prospective study in 377 singleton pregnancies. 298 were normal pregnancies and 79 were spontaneous abortions, the latter of which were viable in 18 cases at the time of examination and non-viable in 61 cases. With a reliable gestational age between 5 and 10 weeks, the yolk sac was recognized in 158 of 172 normal pregnancies (91.9%), in all 14 viable but later aborted pregnancies, but only in 10 of 29 non-viable pregnancies (34.5%) (p less than 0.0000005). With a mean diameter of the chorionic cavity between 5 and 50 mm, the yolk sac was identified in 237 of 253 normal gestations (93.7%), in 16 of 18 viable but later aborted gestations (88.9%), but only in 14 of 41 non-viable gestations (34.1%) (p less than 0.0000001). A diameter of the yolk sac above 6 mm was observed in 5 of 253 normal pregnancies (2.0%), but in 7 of 29 spontaneous abortions (24.1%) (p less than 0.00005). A diameter above 7 mm was not seen in any instance of normal development but in 4 of the pathological courses (13.8%) (p less than 0.0001). It is concluded, that a yolk sac which is not visible in vaginal sonography between 5 and 10 complete weeks menstrual age or a chorionic cavity diameter between 5 and 50 mm and a yolk sac diameter above 6 mm can serve as indicators of a developmental disturbance in early pregnancy.