Fetal breathing movements

Posted byBrian Hopkins

First identified in 1888, they are rhythmical, but paradoxical, chest wall and abdominal movements, which are the precursors of postnatal respiration.  Appearing for the first time between the gestational ages of 10-16.5 weeks, they do not result in gas exchange with the lungs, and their early onset in prenatal life suggests they serve to promote the development of lung tissue in preparation for postnatal life.  During such movements, no amniotic fluid enters the lungs.  Their rate (e.g., more 100 per hour after 13 weeks) is, unlike other fetal movements, related to glucose intake after maternal food ingestion.  They increase in rate as pregnancy progresses, and show a delay of one week in their appearance with feetuses of diabetic mothers.  The figure below shows changes in the number of breathing movements from 8 to 36 weeks gestational age.

Number of fetal breathing movements derived from one-hour ultrasound recordings from 8 to 36 weeks. Note the large increase in number after 24 weeks. The black line stands for the median and the gray lines for the interquartile range. Figure adapted from de Vries, J.I.P., Visser, G.H.A., & Prechtl, H.F.R. (1985). The emergence of fetal behaviour. II. Quantitative aspects. Early Human Development, 15, 333-34 8 for 8 to 19 weeks, and from Roodenburg, P.J., Wladimiroff, J.W., van Es, A., & Prechtl, H.F.R. (1991). Classification and quantitative aspects of fetal movement during the second half of pregnancy. Early Human Development, 25, 19-35 for 20 to 36 weeks.  

See Amniotic fluid, General movements, Gestational age, Hiccups, Stretches, Startles