PATTERNS OF BREATHING MOVEMENTS IN THE NEAR-TERM HUMAN FETUS - RELATIONSHIP TO BEHAVIORAL STATES

The occurrence of fetal breathing movements was studied in relation to fetal behavioural states 1F and 2F, as recognized by the heart rate p atterns A and B, respectively, Simultaneous recordings of fetal heart rate and body, eye and breathing movements were available for analysis (n = 88). These recordings, lasting greater-than-or-equal-to 2 h, had been made in healthy near-term fetuses during the afternoon or evenin g, starting about 1 h after the maternal meal. In the majority of reco rdings fetal breathing activity was lower during heart rate pattern A than during pattern B, but as the opposite occurred in 29/88 recording s (33%), the interstate difference was not significant (P = 0.052). De tailed analysis revealed that breathing movements were more numerous d uring pattern B than during pattern A if the incidence of breathing du ring a particular time period was low (30-40% of time). At a high over all breathing incidence (>40%), however, breathing movements were more often present during pattern. A than during pattern B. The latter occ urred especially in the first hour of recording, i.e. less distant in time from maternal meals. We conclude that fetal breathing activity is generally higher during state 2F than during state 1F, but a clear-cu t state-dependency is absent. Secondly, the relationship between the i ncidences of breathing during states 1F and 2F depends on the 'drive' or motivation (presumably the blood glucose content) to breathe.