Effects of sustained hypoxemia on the sheep fetus at midgestation: endocrine, cardiovascular, and biophysical responses.
OBJECTIVE
The purpose of our study was to examine the effects of induced hypoxia on endocrine, cardiovascular, and biophysical measurements of the ovine fetus at 0.6 (83 to 93 days) of gestation and to compare the fetal responses at this earlier gestation with those reported near term.


METHODS
Fourteen fetal sheep were studied (9 in the hypoxia group and 5 in the control group) at 0.6 of gestation during a 24-hour control period, 8 hours of either sustained hypoxemia or room air, and a 40-hour recovery period.


RESULTS
Induced fetal hypoxemia resulted in a progressive lactic metabolic acidosis; however, all fetuses had recovered within 24 hours. The fetal endocrine response was variable with norepinephrine, the only measured hormone showing a significant hypoxia-related increase (p less than 0.05). Fetal heart rate and mean arterial blood pressure showed little hypoxia-induced change, although fetal heart rate was significantly increased over the first 2 hours (p less than 0.05). The percent time fetal breathing movements, electroocular activity, and nuchal muscle activity likewise showed little hypoxia-induced change.


CONCLUSIONS
The cardiovascular and biophysical response of the preterm fetus to induced hypoxemia is thus much less pronounced than that of the older gestational-aged fetus; this difference may impact on survival and the success of antenatal assessment protocols.
Matsuda
Y
Y
Department of Obstetrics and Gynaecology, Kagoshima Medical School, Japan.
Patrick
J
J
Carmichael
L
L
Challis
J
J
Richardson
B
B
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002245:Carbon Dioxide / Q000097:blood; D002319:Cardiovascular System / Q000503:physiopathology*; D004702:Endocrine Glands / Q000503:physiopathology*; D005260:Female; D005315:Fetal Diseases / Q000503:physiopathology*; D005865:Gestational Age; D006728:Hormones / Q000097:blood; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology*; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D010100:Oxygen / Q000097:blood; D011247:Pregnancy; D012756:Sheep / Q000196:embryology
D001786:Blood Glucose; D006728:Hormones; D007773:Lactates; D002245:Carbon Dioxide; D019344:Lactic Acid; D010100:Oxygen