Velocimetric and biochemical fetal effects of placental embolisation using microspheres in ewes

To investigate the reliability of our animal model and study the fetal response to placental ischemia.

Eight monofetal pregnant ewes were fitted with appliances in conformity with a previously defined operating protocol which we have developed. Microspheres at different concentrations were injected through the fetal face of the placenta. The extent of this embolisation was evaluated using biochemical (acid-base balance) and velocimetric criteria (umbilical and carotid arteries).

Five fetuses received high concentrations of microspheres and developed acute fetal distress (pH = 6.8 +/- 0.05; PO2 = 6.7 +/- 0.4; (S - D)/S (U.A.) = 1.0; (S - D)/S (C.D.) = 0.58 +/- 0.05). Three fetuses received lower concentrations of microspheres and developed chronic fetal distress (pH = 7.2 +/- 0.02; PO2 = 15 +/- 1; (S - D)/S (U.A.) = 0.75 +/- 0.09; (S - D)/S (A.C.) = 0.62 +/- 0.04).

Our experimental model is able to reproduce acute and chronic fetal distress. The concentration of microspheres used to create chronic distress is currently understood. Long-term fetal compensation mechanisms prevent the evaluation of risks linked to each degree of chronic distress in utero. The subsequent aim is to obtain a correlation between velocimetric observations and acid-base balance data.