Three dimensional ultrasound volumetry - new perspectives in prenatal diagnosis

Three-dimensional (3D) ultrasound is a relatively new technique that has one of its most important domains in prenatal diagnosis. Using this method fetal anatomical details can be viewed three-dimensionally at an early stage of pregnancy. Additionally, volumes of various structures can be calculated. To date no major study about 3D- ultrasound-volumetry in prenatal diagnosis has been published. Therefore it is the aim of this project to evaluate the possibilities of this method on a large number of pregnancies. For this purpose two focal points have been set, volumetry of the placenta and of the fetal body. Placental volumetry: A low placental volume could be (even in first trimester) a predictor for intrauterine growth restriction or pregnancy complications. The underlying mechanism could be that due to failing trophoblast invasion the volume of the placenta stays small and complications during the course of pregnancy occur. This hypothesis was supported by two studies with relatively few patients in which it was found that pregnancies with low midtrimester placental volume have a higher risk for birth of a small for gestational age baby. This project aims both to evaluate existing results on a large number of patients and to investigate further connections between a decreased (or also an increased) placental volume and various pregnancy complications. Possibly, this leads to new methods in the early detection of risk-pregnancies. Also placental volume in the first trimester should be investigated because no work about this was published to date. Fetal volumetry: In a group of 64 pregnant women it was shown that a low midtrimester fetal body volume, in combination with a low growth rate between first and second trimester, is correlated with a higher rate of pregnancy complications. Associations might exist between suboptimal fetal supply (maybe due to incipient placental insufficiency) and an early growth restriction on the one hand and later pregnancy complications on the other hand. We also plan to investigate this hypothesis during the proposed project. In addition to fetal volume other data that are routinely obtained should be included. These are uterine artery velocimetry, nuchal translucency measurement, and first and second trimester biochemical testing parameters. We shall investigate whether a combined occurence of aberrant fetal or placental volume and "adverse" parameters leads to a better predictive value of 3D-volumetry. This study will be undertaken at Vienna`s Danube Hospital on approximately 2500 to 3000 pregnant women. Volumetric measurements will be performed during the 12th , the 17th and the 22nd week of gestation and follow- up will be done until birth.

The aim of this project was to ascertain the value of volume measurements - by using three-dimensional (3D) ultrasound during pregnancy. Both, placental and fetal body volume were determined. Whereas for the latter the only relevant result we could find was an association between fetal volume growth rate in early pregnancy and the actual birth weight, referring to placental volume measurements, a number of interesting findings could be discovered: - Placental volume in early pregnancy is correlated to various placenta-depending hormones (like pregnany- associated plasma protein A, PAPP-A). - The birthweight is associated with placental volume as well. - Correlations with more tested measurements (like perfusion of the uterine arteries) could be established. The main advantage of placental volume measurements is the fact that it can be determined in a much earlier phase of pregnancy. - Associations with placenta-depending diseases (e.g. HELLP-syndrome, preeclampsia) could be established as well. - Furthermore we could find out that in the first trimester the placental volume in pregnancies with chromosomal anomalies (e.g. trisomy 21, trisomy 13, trisomy 18) is often much smaller than in those which are not affected. - Of interest is the fact that placental volume growth appears to show differences between the various kinds of placenta-associated pregnancy complications. Concluding, on the one hand new details of placental pathophysiology could be found. On the other hand it seems to be possible that improvements in pregnancy screening and surveillance can be made. Because of the large number of data deriving from this study, analysis und further evaluation still continues. However, placental measurement has been introduced into the routine program at the Donauspital in the meantime.