Fetal circulatory responses during maternal bleeding

The purpose of this study was to investigate the fetal circulatory responses during maternal hemorrhage. Five pregnant goats with fetuses with a mean gestational age of 132 +/- 2 days were used. The maternal blood was withdrawn at 350 ml/h for 2 hours (e.g. 700 ml, 11.9 ml/kg maternal weight) and reinfused at the same speed. During maternal bleeding, maternal arterial pressure (MAP) gradually decreased. As a result of this maternal hypotension, fetal arterial pO2 and pH decreased, and PCO2 increased. After the reinfusion, fetal pO2 recovered but pH and PCO2 did not recover. Fetal arterial pressure (FAP) increased and heart rate (FHR) decreased during maternal bleeding and returned to the control level, after the reinfusion. Fetal arginine vasopressin (AVP) concentration increased to 401.2 +/- 318.5 pg/ml at the maximum bleeding. There were significant positive correlation between AVP concentration and FAP, and negative correlation between AVP and FHR during maternal bleeding. Therefore, we concluded that 700 ml maternal bleeding for 2 hours resulted the decrease in fetal pH, pO2, and FHR, and increase in PCO2, FAP, and AVP concentration. Fetal pH, PCO2, and AVP did not return to the control level in spite of reinfusion.