Fourth World Conference on Early Pregnancy CONTINUUM BETWEEN IMPLANTATION AND PERINATAL EVENTS

Volume And Vascularity Of The Yolk Sac Assessed By Three-Dimensional And Power Doppler Ultrasound

S. Kupesic, A. Kurjak

Department of Obstetrics and Gynecology, Medical School University of Zagreb, Sveti Duh Hospital, Zagreb, Croatia

Presentation

The yolk sac is an organ of increasingly recognized importance in the initial mechanisms of pregnancy maintenance and the early growth and welfare of the embryo. The aim of our study was to assess the vascularity of the yolk sac and vitelline duct in 150 patients between the 6^th and 10^th weeks of normal, and uncomplicated pregnancies who were scheduled for termination of pregnancy for psychosocial reasons and 130 complicated pregnancies. In same patients volume of the yolk sac was assessed using Combison 530 3D Voluson, Medison-Kretz Company.

Overall visualization rate for yolk sac vessels was 80,38%. The highest visualization rates were obtained in the 7th and 8th weeks of gestation reaching values of 90,71 %. In the same period the visualization rates of the vitelline duct arteries were 87,71% and 91,28% respectively. A characteristic waveform profile included low velocity (5,8+/-1,7 cm/s) and absence of diastolic flow which was obtained from all examined yolk sacs. The PI showed the mean value of 3,24+/-0,94 without significant changes between subgroups (p>0,05). Vitelline vessels showed similar PSV (5,4+/-1,8 cm/s) and PI values (3,14+/0,91) (p>0,05) to that obtained from the yolk sac.

Three types of abnormal vascular signals were derived from the yolk sac in patients with missed abortion (n=32): irregular blood flow (n=6), permanent diastolic flow (n=2) and venous blood flow signals (n=5). However, in the most of the patients (n=19) blood flow signals could not have been extracted from these early embryonic structures.

Using three-dimensional ultrasound we found a positive correlation between gestational age and volumes of the gestational and yolk sac until 10 weeks' gestation. At the end of the first trimester yolk sac volume remained constant, while gestational sac volume continued to grow.

It seems that changes in both yolk sac appearance (size, shape, volume and echogenicity) and vascularization are probably a consequence of poor embryonic development or even embryonic death, rather than being a primary cause of an early pregnancy failure.

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