Ultrasonographic patterns of fetal breathing movements in normal pregnancy

Objective: To assess through pregnancy fetal breathing movements (FBMs) patterns detected by M-mode and Doppler velocimetry technology. Methods: In this cross-sectional study FBMs were investigated in 1882 uncomplicated pregnancies over a 4-year period. Abdominal and thoracic wall movements of fetuses between 14 and 40 weeks of gestation were studied by M-Mode scan, and color Doppler velocimetry with spectral imaging analysis was used to investigate the presence of FBMs associated with nasal fluid flow velocity waveforms (NFFVWs). Results: Abdominal movements were observed in 19% of cases when gestation was less than 20 weeks and in 61% of cases when it was between 21 and 25 weeks; chest movements were significant after 21 weeks; and NFFVWs were detected at 22 weeks and increased progressively to 93% of cases at term. Conclusions: Fetal breathing movements are a complex phenomenon with a composite, progressive pattern of development during gestation.