Ultrasound measurements of the diameter of the fetal trachea, larynx and pharynx throughout gestation and applicability to prenatal diagnosis of obstructive anomalies of the upper respiratory-digestive tract

The purpose of the present study was to obtain normative data for the fetal upper respiratory tract by using high-resolution ultrasound techniques. Fu rthermore, we wanted to test the potential utility of the resulting normogr ams in diagnosing obstructive lesions of the trachea and oesophagus. Sonogr aphic measurements of the diameters of the trachea, larynx and pharynx were obtained at well-defined planes from a prospective cross-sectional sample of 198 normal patients of known gestational age between 15 and 40 weeks' ge station. All measurements were performed during fetal apnea and in the abse nce of swallowing. The same measurements were also obtained from two cases with laryngeal atresia and three cases with oesophageal atresia, all of whi ch were diagnosed prenatally. The data obtained were plotted on the constru cted normo rams. In normal fetuses approximately linear relationships exist ed between tracheal, laryngeal and pharyngeal diameter, on the one hand, an d gestational age, on the other, with the measurements correlating signific antly (p <0.0001) with gestational age. The linear regression coefficients (r(2)) for the tracheal, laryngeal and pharyngeal diameters were 0.66, 0.55 and 0.32, respectively. The 95 per cent prediction limits were also calcul ated. In fetuses with laryngeal atresia only the tracheal diameter was sign ificantly higher as compared with that of normal fetuses. Data of the fetus es with oesophageal atresia showed that there were no changes in the upper airway anatomy. Our study provides normative data for the upper respiratory tract. In the prenatal diagnosis of obstructive neck anomalies the usefuln ess of the data would seem to be limited to those affecting the respiratory tract. Among the structures measured, only the trachea may prove to be of clinical significance. Copyright (C) 1999 John Wiley & Sons, Ltd.