Observation and measurement of trachea and bronchus in normal fetuses by prenatal ultrasonography

Abstract

Objective To explore the methodology of observing trachea and bronchus in the normal fetuses by prenatal ultrasound and to summarize its ultrasonographic features, then to measure relevant parameters and to establish their normal reference value range. Methods Nine hundred and seventy normal fetuses from 20 to 39+ 6 weeks of gestation were observed by ultrasound at the coronal section of trachea and bronchus.The subjects were classified into five groups according to gestational age to calculate demonstration rate: group A, 20-23 weeks; group B, 24-27 weeks; group C, 28-31 weeks; group D, 32-35 weeks, group E, 36-39 weeks. The fetuses whose trachea and bronchus were clearly shown were grouped by each gestational week to measure the diameters of trachea and left/right bronchus and the angle between them. Results There were 565 fetuses whose trachea and bronchus could be demonstrated clearly (58.2%). The numbers and demonstration rates of each group were following: group A 184(53.5%), group B 88(79.3%), group C 109(68.1%), group D 97(48.3%) and group E 87(55.4%). The results of both group B and C were significantly higher than others (P 0.05). The angle between trachea and left bronchus was smaller than that of trachea and right bronchus(P<0.05). Conclusions It is feasible to observe fetal trachea and bronchus at the coronal view of thorax. The appropriate gestational age for ultrasonic observation is 24-31+ 6 weeks. The diameter of trachea and bronchus and the angle between them can be potential valuable for assessing the growth of trachea and bronchus prenatally. The fact that the angle between trachea and left bronchus was smaller than that of trachea and right bronchus may provide a new clue for judging visceral position. Key words: Ultrasonography, prenatal; Fetus; Trachea; Bronchi