EP05.10: Transverse diameter of thymus in second trimester of pregnancy by 2D ultrasound: normogram of Indian fetuses

Abstract

The thymus has been studied in fetuses as an additional marker of DiGeorge Syndrome. Recently, it has also been associated with prolonged premature rupture of membranes and intrauterine growth restriction (IUGR). We have carried out this study to develop a normogram of the thymus transverse diameter (TTD) in second trimester of pregnancy by 2D ultrasound in Indian fetuses. The present study is prospective and cross sectional. The TTD was measured by placing a line cursor perpendicular to the line connecting the spine and sternum in normal fetuses between 18 to 28 weeks of gestation using GE Volusion E10-BT/E8-BT 13.5 ultrasound device with a transabdominal C5-9, 9L, RAB6-D transducers at Paras advanced centre for fetal medicine between January 2017 and September 2017. The relationship of TTD with the gestational age was assessed by using general linear regression modelling. Centile curves were calculated using mean (μ) and standard deviation (SD). A total of 330 normal fetuses were included. TTD increased with increasing gestational age in a linear manner. Regression equations were μ = 0.0544x2 - 1.2903x + 17.326 and SD = -0.038x2 + 1.8184x - 19.27 respectively. The predicted mean and 1st, 5th, 10th, 50th, 90th, 95th and 99th centile reference ranges of TTD at each gestational age are shown in graph below. We have created a normogram for TTD on 2D-US in Indian fetuses of 18-28 week of gestation. This will help us identify a possible association of thymic hypoplasia with Di-George syndrome and Trisomy 18 and 21. Supporting information can be found in the online version of this abstract Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.