In utero development of fetal breathing movements in C57BL6 mice.

Fetuses of many species, including humans, breathe during development. This fetal breathing aids in lung development, strengthens respiratory muscles, and is posited to fine-tune the neural circuitry that drives breathing. Previous studies suggested that fetal breathing could begin as early as the fifteenth day of gestation in the mouse, but fetal breathing movements (FBMs) had not been observed in mice in utero.