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Our aim was to identify patterns of fetal perinasal fluid flow, and to determine the relationship of pattern of flow to the diaphragmatic component of fetal breathing movements. Twenty-four fetuses were studied with the use of two ultrasound systems simultaneously. Continuous video-tape records of the color and spectral Doppler imaging of fluid flow velocity in the nose and of the movements of the fetal diaphragm were made on two video recorders during 30-min study sessions. Two different patterns of fetal perinasal flow were recognized. One type had a rapid rate and low amplitude, and was independent of ultrasonographically observed movements of the fetal diaphragm. The other type had a lower rate and higher amplitude, and was uniformly related to diaphragmatic contractions. The breath-to-breath interval, time of inspiration, time of expiration and peak inspiratory and expiratory velocities were determined for each type of perinasal flow. Two ratios were used to quantify the change of peak flow velocity. There were significant differences in the values of all timing parameters between diaphragm-related perinasal flow velocities and those not related to the diaphragm, at both 30-36 and 37-41 weeks of gestation. The rate of perinasal flow related to diaphragmatic contraction cycles was one-third that of the flow cycles not related to diaphragmatic contraction (approximately 50 vs. 148 cycles/min). For both patterns of perinasal flow velocity, the expiratory peak velocity ratio was about 1.6 times higher than the inspiratory peak velocity ratio. We conclude that, in uncomplicated pregnancy, one pattern of fetal perinasal fluid flow reflects activity of the diaphragm. We speculate that the contractions of the fetal airway smooth muscle or oropharyngeal-laryngeal muscle groups are the origin of the second pattern of perinasal flow.

Fetal upper respiratory tract function was studied in five cases of antenatally diagnosed congenital diaphragmatic hernia and in 16 cases of uncomplicated pregnancy at gestational ages ranging from 27 to 38 weeks. The evaluation of fetal upper respiratory tract function was performed using ultrasonography combined with color-flow and spectral Doppler analysis. In all cases with uncomplicated pregnancy, fetal breathing-related nasal and oropharyngeal fluid flow was seen at the level of the nose. The five cases with congenital diaphragmatic hernia all demonstrated fetal breathing activity by thoracic wall movement. In four of the fetuses, perinasal fluid flow was seen by the Doppler technique. The fetus with no demonstrated perinasal flow during breathing movements died in the early neonatal period and had pulmonary hypoplasia. Observation of the fetal breathing-related nasal and oropharyngeal fluid flow in cases of antenatally diagnosed congenital diaphragmatic hernia provides a rationale to hypothesize that the absence of this phenomenon is a useful marker for prenatal prediction of pulmonary hypoplasia.

The objective of this review is to discuss the current knowledge of fetal pulmonary hypoplasia and to summarize the clinical significance of the many ultrasound methods for predicting pulmonary hypoplasia in pregnancies complicated by oligohydramnios due to spontaneous rupture of the fetal membranes and in cases complicated by fetal congenital diaphragmatic hernia. We concluded that the presence or absence of polyhydramnios, fetal breathing movements, mediastinal shift, thoracic position of the stomach, fetal breathing-related nasal and oropharyngeal fluid flow, ductal flow velocity modulation, and gestational age at onset and severity of ventricular disproportion as useful markers for predicting fetal pulmonary hypoplasia is a productive area for continued research. All studies show that there is a clear association between most of these markers and pulmonary hypoplasia. However, these markers have not been studied together in a large number of cases, and comparisons between each of the markers is unknown.