Fetal breathing-related nasal fluid flow velocity in uncomplicated pregnancies.

OBJECTIVE

Our purpose was to determine the Doppler ultrasonographic characteristics of fetal breathing-related nasal fluid flow velocity in uncomplicated pregnancies.

STUDY DESIGN

Fetal nasal flow velocity was studied in 52 uncomplicated pregnancies at gestational ages ranging from 22 to 41 weeks. The evaluation of fetal breathing-related nasal fluid flow velocity was performed with ultrasonography combined with color flow and spectral Doppler analysis.

RESULTS

The study revealed that the breath-to-breath interval and duration of the inspiratory phase of the fetal breathing-related nasal flow increased from 22 to 35 weeks and decreased thereafter. The breath-to-breath interval (milliseconds) at 33 to 35 weeks (1203.9 +/- 295.7 SD) was approximately twice what it was in the earliest age group (22 to 25 weeks); subsequently it decreased by approximately 25% in the term group (38 to 41 weeks). A positive correlation existed between the mean breathing-related nasal peak inspiratory flow velocity and advancing gestational age (r = 0.56, p = 0.0008), and between the inspiratory flow velocity acceleration and advancing gestational age (r = 0.53, p = 0.0076).

CONCLUSION

Changes in fetal breathing activity during uncomplicated pregnancies can be determined by measurement of fetal breathing-related nasal fluid flow velocity. Our observations in uncomplicated pregnancies may be useful in future studies of these parameters in complicated pregnancies such as those at risk for pulmonary hypoplasia.