Human fetal respiratory arrhythmia.

The association of human fetal respiration with the fetal heart rate was studied in 13 pregnant patients between Weeks 34 and 41 of pregnancy. Fetal respiration was recorded with the use of a tocodynamometer. Fetal heart rate was recorded with the use of ultrasound and abdominal fetal electrocardiogram monitoring devices. The results documented the presence of human fetal respiratory arrhythmia. An increase in fetal heart rate was seen during fetal "inspiration" followed by a decrease during "expiration." The possible mechanisms of the respiratory arrhythmia are discussed.