Circulatory responses to maternal hyperoxaemia and hypoxaemia assessed non-invasively in fetal sheep at 0.3-0.5 gestation in acute experiments.
OBJECTIVE
To determine fetal haemodynamic responses to hyperoxaemia and hypoxaemia in early pregnancy.


METHODS
Repeated measurements in acute experiments.


METHODS
Experimental physiology laboratory.


METHODS
Non-invasive Doppler ultrasound of the umbilical vein, ductus venosus, umbilical and common carotid arteries of 12 fetal lambs (0.27-0.56 gestation) during maternal hyperoxaemia and hypoxaemia under ketamine anaesthesia. The effect of gestational age, hyperoxaemia, and hypoxaemia were assessed based on analysis of variance for dependent measurements and P < or = 0.05 was considered significant. Differences between groups were considered significant if the 95% confidence interval did not include zero.


RESULTS
Gestational age had a significant effect on the blood velocity in the umbilical vein and ductus venosus. There were no circulatory changes during hyperoxaemia, but a simultaneous increase of pCO2 was an important confounder. However, hypoxaemia caused significantly reduced heart rate, reduced maximum and weighted mean blood velocity, and augmented pulsation in the umbilical vein. Hypoxaemia also caused reduced velocities in the ductus venosus (peak velocity during systole and minimum during diastole, and time-averaged velocity) and augmented pulsation of the flow velocity. Additionally, the pulsatility of blood flow increased in the umbilical artery and was reduced in the common carotid artery.


CONCLUSIONS
Maternal hypoxaemia in early pregnancy causes similar fetal circulatory responses to those in late pregnancy: bradycardia, reduced venous flow velocities, augmented pulsatility in veins and a redistributional flow velocity pattern of the umbilical and common carotid arteries.
Kiserud
T
T
Department of Obstetrics and Gynaecology, Royal Free and University College Medical School, London, UK.
Jauniaux
E
E
West
D
D
Ozturk
O
O
Hanson
M A
MA
D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D017536:Carotid Artery, Common / Q000502:physiology; D005260:Female; D005865:Gestational Age; D006340:Heart Rate, Fetal / Q000502:physiology; D018496:Hyperoxia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D011247:Pregnancy; D011248:Pregnancy Complications / Q000503:physiopathology*; D012756:Sheep; D018608:Ultrasonography, Doppler; D014469:Umbilical Arteries / Q000502:physiology; D014471:Umbilical Veins / Q000502:physiology
D002245:Carbon Dioxide; D010100:Oxygen