Analysis of fetal breathing movements at 30-38 weeks of gestation.

AIMS This study reports the changes in patterns of fetal breathing movements recorded with a photogrammetric method in three successive periods of gestation. METHODS Respiratory movements were studied in fetuses of 28 healthy women with uncomplicated pregnancies of 30-38 weeks of gestation. Women were divided into three groups according to gestational age of the fetus: 30-32 weeks, 7 fetuses; 33-36 weeks, 9 fetuses; and 37-38 weeks, 12 fetuses. Sonographic images of the fetuses were recorded on videotape, digitized (1 image per 0.12 s) and analyzed with specially developed software. RESULTS The proportion of fetuses in each age group for which movements were detectable was similar in all three groups, as was the frequency of movements. Duration of a complete respiratory cycle, the inspiratory phase and the expiratory phase tended to be shorter at 33-36 weeks of gestation than in younger and older fetuses. Fetuses in the 30-32-week group had slower breathing rates than fetuses in the two older groups. CONCLUSIONS The photogrammetric technique revealed differences in some patterns of fetal breathing movements between weeks 30-32, 33-36 and 37-38 of gestation. The data provide a sound basis for relating changes in fetal breathing movements with physiological and anatomical changes that occur as the respiratory system matures.