[Normalization of fetal heart rate and fetal blood pressure following reduction of uterine blood circulation]

Abstract

To analyze the variability of fetal heart rate (FHR) after a temporary definite hypoxia, uterine blood flow (QUT) was totally reduced in 8 pregnant sheep. In 13 experiments the reduction lasted 60 sec and in 13 further experiments 180 sec. The normalization of FHR after reduction of QUT was compared with the change of fetal blood pressure (BP) and fetal oxygen saturation (SO2).

Results: During reduction of QUT the fall of FHR and the decrease of SO2 was significant (r = -0,43, 2 alpha less than 0,05). With the start of normalization there was a temporary correlation between the increase of FHR and the restauration of SO2 after 12-18 sec (r = 0,79, 2 alpha less than 0,001). Thus the initial rise of FHR might be caused by the chemoreceptors. Above all after longer reduction of QUT there were three typical reactions during the recovery period: increase of FHR and BP, short fall of FHR and BP and increase of FHR and continous fall of BP. The start of normalization of FHR after reduction of QUT depends on the restauration of SO2. Because of the variable FHR response it is not possible to describe the duration of the preceding hypoxia.