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Abstracts 1080 Clinical application of three-dimensional ultrasonography in obstetric management Jun JK, Seoul National University College of Medicine, Korea In obstetrics, ultrasonography is an essential tool in the diagnosis and treatment, including USG-guided invasive procedures. Before ultrasound era, fetal anomaly was only discovered after delivery. With introducing ultrasonography in prenatal care, fetal anomaly has become an important issue in every pregnant woman. Nowadays, most of obstetricians adopt ultrasound examination as a primary step for fetal morphologic and functional evaluation. Two-dimensional ultrasound showed a high sensitivity rate for fetal anomaly detection, especially in high-risk group. However, three-dimensional ultrasonography (3D USG) is a logically more desirable option to delineate structural details because the fetus is three-dimensional. With technical advances, shorter acquisition time and sharper image quality make 3D USG valuable tool to detect fetal anomaly. Moreover, using 3D tomogram, slight changes of each structure can be reevaluated and identified after storing the image. The other advantage of 3D USG is volume measurement. Many volumetric standards were made on the basis of 2D USG. Volume assessment is a strong point of 3D USG especially in irregular structures. After more accurate standards are constructed with 3D USG, they will help us reach more consistent and reasonable decision. Two topics, identification of cleft palate and evaluation of amniotic fluid volume by 3D USG will be shown as an example of new scope of 3D USG application. Cleft lip is a relatively common anomaly easily detected in utero. The incidence of cleft lip is approximately one per 600 live-born infants in Asians. Generally, cleft lip is known to be a mild structural anomaly that leaves no long-term sequelae if correctly repaired postnatally. However, It is reported that the presence of cleft palate in cases affected with cleft palate shows a worse prognosis. When we counsel the woman whose fetus has a cleft lip, whether a cleft is confined to the lip or extended to palate is important. However, accurate determination of cleft palate is not easy. In 3D tomogram, multiple sliced views can be a new option to detect cleft palate in the cases of cleft lip. Amniotic fluid (AF) volume measurement has been thought important in predicting fetal well-being and many approaches have been proposed to assess AF volume. Single deepest pocket and amniotic fluid index are most commonly used. However, they have limitations especially in borderline oligohydramnios or polyhydramnios. To evaluate amniotic fluid, we constructed a normogram of hourly fetal urine production rate (HFUPR) according to gestational age by measuring bladder volume change with 3D USG. In cases of borderline oligohydramnios, normal HFUPR means normal renal perfusion that comes from adequate uteroplacental perfusion. It may defer delivery. In cases of borderline polyhydramnios, increased HFUPR means high production polyhydramnios, while normal HFUPR suggests decreased fetal intake and/or absorption. It is a good example of functional evaluation with 3D USG. From now on, it is expected that 3D USG can play a critical role in the management of pregnant women although it is currently being used as an adjunct to 2D USG, especially in morphologic evaluation.
FETAL ANOMALY 1081 Does prenatal diagnosis make a difference? Copel JA, Yale University School of Medicine, United States of America Despite decades of use, there has been little data available on postnatal outcomes in anomalous infants comparing those prenatally versus
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postnatally diagnosed. In this lecture, we will review the literature with particular attention to congenital heart disease, which is an excellent model for study due to the high morbidity and mortality associated with these conditions. 1082 Genetic ultrasound: Assessing the risk of Down syndrome Benacerraf BR, Harvard Medical School, United States of America Objective: The objective of the lecture will be to discuss how to interpret the risk of Down syndrome in fetuses with sonographic markers both isolated and in combination using Bayes theorem and likelihood ratios. Materials: We will discuss several different studies that evaluate the use of the genetic sonogram on fetuses presenting between 15 to 20 weeks gestation. The following markers and findings are sought by most investigators: major structural defects, nuchal fold, short long bones, pyelectasis, echogenic intracardiac focus and hyperechoic bowel. The sensitivity, specificity and likelihood ratios (LR) for each of the sonographic markers, when isolated or in combination, are used to modify the a priori Down syndrome risk. The method for doing this modification will be demonstrated. Results: Combining several studies, the presence of any marker results in the sensitivity for detecting Down syndrome of 70% to 80 % with a false positive rate of 8% to 12.4 %. The absence of any markers conferred a likelihood ratio of 0.2 to 0.3, decreasing the baseline risk of Down syndrome by 70% to 80%. The nuchal fold is the most sensitive and specific marker, carrying a high likelihood ratio of ⬎12. Other isolated markers had lower likelihood ratios due to the higher prevalence in the normal population. The likelihood ratios for the presence of more than one minor marker in the same fetus are higher than the product of the individual likelihood ratios, (six depending on the combination and number of markers). Conclusion: Sonographic features of DS carry different likelihood ratios, which can be used to adjust the patient’s a priori risk of DS, thus providing a more patient specific risk of aneuploidy. Clusters of markers confer a higher risk than isolated markers. This approach to the second trimester scan can be used to modify prior risk from quadruple serum screen and even first trimester risk results. 1083 First trimester malformation Meagher SE, Monash Ultrasound for Women, Australia First trimester ultrasound is a valuable tool in early pregnancy dating. More recently, high resolution ultrasound has been employed to assess the nuchal translucency risk estimation of aneuploidy between 11 and 14 weeks gestation. Transvaginal ultrasound at this time also provides the opportunity to assess embryonic and early fetal structure and has proven to be a valuable tool in the early detection of many structural abnormalities. • Many abnormalities previously detected as late as 18 to 20 weeks may now be visualised at transvaginal ultrasound as early as 9 to 10 weeks gestation, i.e., 7 to 8 weeks following conception. While many first trimester anomalies have sonographic features similar to those ascribed in the second and third trimester of pregnancy, others have characteristic sonographic features confined to the first trimester. • There are many practical and psychological benefits to the early diagnosis of fetal malformation. Earlier prenatal diagnosis may provide the opportunity for early prenatal medical and interventional therapies which may in the future lead to improved fetal outcome. The appropriate interpretation of first trimester ultrasound however requires an in depth knowledge of sonoembryology and the pathophysiology of fetal malformation.
FETAL ANOMALY 1081 Does prenatal diagnosis make a difference? Copel JA, Yale University School of Medicine, United States of America Despite decades of use, there has been little data available on postnatal outcomes in anomalous infants comparing those prenatally versus
P27
postnatally diagnosed. In this lecture, we will review the literature with particular attention to congenital heart disease, which is an excellent model for study due to the high morbidity and mortality associated with these conditions. 1082 Genetic ultrasound: Assessing the risk of Down syndrome Benacerraf BR, Harvard Medical School, United States of America Objective: The objective of the lecture will be to discuss how to interpret the risk of Down syndrome in fetuses with sonographic markers both isolated and in combination using Bayes theorem and likelihood ratios. Materials: We will discuss several different studies that evaluate the use of the genetic sonogram on fetuses presenting between 15 to 20 weeks gestation. The following markers and findings are sought by most investigators: major structural defects, nuchal fold, short long bones, pyelectasis, echogenic intracardiac focus and hyperechoic bowel. The sensitivity, specificity and likelihood ratios (LR) for each of the sonographic markers, when isolated or in combination, are used to modify the a priori Down syndrome risk. The method for doing this modification will be demonstrated. Results: Combining several studies, the presence of any marker results in the sensitivity for detecting Down syndrome of 70% to 80 % with a false positive rate of 8% to 12.4 %. The absence of any markers conferred a likelihood ratio of 0.2 to 0.3, decreasing the baseline risk of Down syndrome by 70% to 80%. The nuchal fold is the most sensitive and specific marker, carrying a high likelihood ratio of ⬎12. Other isolated markers had lower likelihood ratios due to the higher prevalence in the normal population. The likelihood ratios for the presence of more than one minor marker in the same fetus are higher than the product of the individual likelihood ratios, (six depending on the combination and number of markers). Conclusion: Sonographic features of DS carry different likelihood ratios, which can be used to adjust the patient’s a priori risk of DS, thus providing a more patient specific risk of aneuploidy. Clusters of markers confer a higher risk than isolated markers. This approach to the second trimester scan can be used to modify prior risk from quadruple serum screen and even first trimester risk results. 1083 First trimester malformation Meagher SE, Monash Ultrasound for Women, Australia First trimester ultrasound is a valuable tool in early pregnancy dating. More recently, high resolution ultrasound has been employed to assess the nuchal translucency risk estimation of aneuploidy between 11 and 14 weeks gestation. Transvaginal ultrasound at this time also provides the opportunity to assess embryonic and early fetal structure and has proven to be a valuable tool in the early detection of many structural abnormalities. • Many abnormalities previously detected as late as 18 to 20 weeks may now be visualised at transvaginal ultrasound as early as 9 to 10 weeks gestation, i.e., 7 to 8 weeks following conception. While many first trimester anomalies have sonographic features similar to those ascribed in the second and third trimester of pregnancy, others have characteristic sonographic features confined to the first trimester. • There are many practical and psychological benefits to the early diagnosis of fetal malformation. Earlier prenatal diagnosis may provide the opportunity for early prenatal medical and interventional therapies which may in the future lead to improved fetal outcome. The appropriate interpretation of first trimester ultrasound however requires an in depth knowledge of sonoembryology and the pathophysiology of fetal malformation.