A method for making chronic fetal preparation in the lamb: results of 4 year's experiences

During the period between 1980 and 1983, a versatile experimental model for fetal physiology (chronic fetal preparation) was made using 26 pregnant Corriedale and Suffolk sheep. The sheep fetuses were removed from the uterus at the gestational ages of from 96 to 133 days. After performing cannulation of the carotid arteries, the jugular veins , and the trachea of the fetuses, applying tripolar cardioelectrodes, and attaching an occluder of the umbilical cord, the fetuses were returned to the uterus to complete the gestational period. The time left until the termination of the postoperative pregnancy and available for various intrauterine monitoring procedures varied from 3 to 800 hr. Eleven sheep (42.3%) continued their postoperative intrauterine term for 5 days or more. The continuation of the postoperative gestation for longer than 5 days indicated a return to the physiological state on the evidence of the measured PO2, PCO2 and pH values and rapid irregular breathing movements.