Fetal breathing movements in the normal and growth-retarded human fetus: a multiscan/M-mode echofetographic study

52 women were examined, between the 25th and 40th wk of pregnancy, during the day-time, by the echographic multiscan/M-mode technique. Definitions of normal fetal breathing movements and singultus fetalis movements were determined. In normal pregnancies fetal breathing movements occurred during 12-19% of the total observation time before the 39th wk of pregnancy but only during 6-9% of the observation time in the 39th or 40th wk. In low birth weight pregnancies fetal breathing movements occurred during 8-13% of the total observation time, and the incidence was the same before and after the 39th wk. Singultus fetalis movements occurred in normal and low birth weight pregnancies.