Recently, Kupesic and associates performed a transvaginal colour Doppler study of yolk sac vascularization and volume estimation by 3D ultrasound. They examined 150 patients whose gestation age range from 6 to 10 weeks from the last menstrual period during normal uncomplicated pregnancy. Transvaginal 3D and power Doppler examination was performed before the termination of pregnancy for psychosocial reasons. The highest visualization rates for yolk sac vessels were in the 7th and 8th weeks of gestation, reaching value of 90.71%. a characteristic waveform profile included low velocity, and the absence of diastolic flow was found in all the examined yolk sacs. The pulsatility index showed a mean value of 3.24 ± 0.94 without significant change between subgroups. The author found a positive correlation between gestational age and volumes of the yolk sac until 10 week gestation. At the end of the first trimester, yolk sac volume remained constant, while gestational sac volume continued to grow. 3D ultrasound may significantly contribute to in vivo observation of the yolk sacs “honeycomb” surface pattern.
Increased echogenicity of the yolk sac walls were reported as a sign of dystrophic change that occur in a nonviable cellular material indicating early pregnancy loss. Automatic calculation will allow us to estimate precise relationship between the yolk sac volume and CRL measurement. Kupesic and coworkers measured gestational sac volume and yolk sac volume and vascularity in eighty women with uncomplicated pregnancy between 5 and 12 weeks of gestation. Regression analysis revealed an exponential growth of the gestational sac volume throughout the first trimester of pregnancy. Gestational sac volume measurement can be used for estimation of the gestational age in early pregnancy. Abnormal gestational sac volume measurement could potentially be use as a prognostic marker for pregnancy outcome. Yolk sac volume was found to increase from 5 to 10 weeks of gestation. However, when the yolk sac reaches its maximum volume at around 10 weeks, it has already started to degenerate; which can be indirectly proved by a significant reduction in visualization rates of the yolk sac vascularity.
As suggested earlier, the disappearance of the yolk sac in normal pregnancies is, probably, the result of yolk sac degeneration rather than of a mechanical compression of the expanding amniotic cavity. These events suggest that the evaluation of the biological function of the yolk sac by measuring the diameter and/or the volume is limited. Therefore, a combination of functional and volumetric studies is necessary to identify some of the more important moment during early pregnancy.
Kurjak et al reported vascularization ot the yolk sac in normal pregnancies between 6 and 10 weeks of gestation. Pulsed Doppler signal characterized by low velocity and high pulsatility were obtained in 85.71 percent of the yolk sacs during 7th and 8th gestational weeks. Although the reports on yolk sac and vitelline circulation are very exiting, it should be noted that such studies are not ethically feasible in ongoing human pregnancies since secondary yolk sac is a source of primary germ cells and blood stem cells.
Three-dimensional ultrasound and power Doppler will allow as to study turgescent blood vessels withstanding from the surface of the yolk sac. The same technique can be used to study evolution from the embryo-vitelline towards embryo placental circulation. Since yolk sac and vitelline blood vessels are prerequisite for the oxygen transfer, absorptive and transfer processes during the first trimester, alteration in this early circulatory system may have some prognostic value for predicting pregnancy outcome.
Increased echogenicity of the yolk sac walls were reported as a sign of dystrophic change that occur in a nonviable cellular material indicating early pregnancy loss. Automatic calculation will allow us to estimate precise relationship between the yolk sac volume and CRL measurement. Kupesic and coworkers measured gestational sac volume and yolk sac volume and vascularity in eighty women with uncomplicated pregnancy between 5 and 12 weeks of gestation. Regression analysis revealed an exponential growth of the gestational sac volume throughout the first trimester of pregnancy. Gestational sac volume measurement can be used for estimation of the gestational age in early pregnancy. Abnormal gestational sac volume measurement could potentially be use as a prognostic marker for pregnancy outcome. Yolk sac volume was found to increase from 5 to 10 weeks of gestation. However, when the yolk sac reaches its maximum volume at around 10 weeks, it has already started to degenerate; which can be indirectly proved by a significant reduction in visualization rates of the yolk sac vascularity.
As suggested earlier, the disappearance of the yolk sac in normal pregnancies is, probably, the result of yolk sac degeneration rather than of a mechanical compression of the expanding amniotic cavity. These events suggest that the evaluation of the biological function of the yolk sac by measuring the diameter and/or the volume is limited. Therefore, a combination of functional and volumetric studies is necessary to identify some of the more important moment during early pregnancy.
Kurjak et al reported vascularization ot the yolk sac in normal pregnancies between 6 and 10 weeks of gestation. Pulsed Doppler signal characterized by low velocity and high pulsatility were obtained in 85.71 percent of the yolk sacs during 7th and 8th gestational weeks. Although the reports on yolk sac and vitelline circulation are very exiting, it should be noted that such studies are not ethically feasible in ongoing human pregnancies since secondary yolk sac is a source of primary germ cells and blood stem cells.
Three-dimensional ultrasound and power Doppler will allow as to study turgescent blood vessels withstanding from the surface of the yolk sac. The same technique can be used to study evolution from the embryo-vitelline towards embryo placental circulation. Since yolk sac and vitelline blood vessels are prerequisite for the oxygen transfer, absorptive and transfer processes during the first trimester, alteration in this early circulatory system may have some prognostic value for predicting pregnancy outcome.
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