Adaptation at birth

Before the onset of labor the respiratory system is fluidfilled (Chapter 3) and receives less than 10 percent of the cardiac output.59 Recent studies using three-dimensional ultrasound techniques have shown that the fetal fluid FRC at term is close to the functional residual capacity (FRC) of the neonate after adaptation.5 Although there is great variability, the median time for the onset of respiratory effort is in the region of 10 seconds,64 some infants commencing respiratory efforts immediately the thorax is released from the birth canal.