Measures of acidosis with repetitive umbilical cord occlusions leading to fetal asphyxia in the near-term ovine fetus.
OBJECTIVE
Increasing frequency of severe variable decelerations is associated with acidemia. However, there is little understanding of its development or normalization rate.


METHODS
To quantify the time course of acidemia, 10 near-term fetal sheep underwent a series of mild (1 minute every 5 minutes), moderate (1 minute every 3 minutes), and severe (1 minute every 2 minutes) umbilical cord occlusions (UCO), lasting 1 hour each or until fetal arterial pH decreased to less than 7.00.


RESULTS
Each minute of UCO resulted in base deficit (BD) and lactate increases at rates of 0.56 and 0.35 mmol/L per minute, respectively. During a 2 h recovery, BD and lactate normalized at rates of 0.09 and 0.04 mmol/L per minute. BD correlated highly with lactate (r = 0.95; P < .001).


CONCLUSIONS
Our findings in the near-term ovine fetus suggest that the knowledge of fetal BD deterioration and recovery rates can aid assessing fetal acidemia during labor.
Frasch
Martin G
MG
Department of Obstetrics and Gynecology, Lawson Health Research Institute, University of Western Ontario, London, ON, Canada.
Grasch
Martin G
MG
Frasch
Martin G
MG
Mansano
Roy Z
RZ
McPhaul
Laron
L
Gagnon
Robert
R
Richardson
Bryan S
BS
Ross
Michael G
MG
D000138:Acidosis / Q000175:diagnosis*; D000818:Animals; D005260:Female; D005311:Fetal Hypoxia / Q000209:etiology / Q000503:physiopathology*; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012756:Sheep; D047929:Term Birth; D014470:Umbilical Cord / Q000098:blood supply*