Fetal Brain Damage Following Maternal Carbon Monoxide Intoxication: An Experimental Study

Techniques of fetal monitoring, including fetal blood sampling in utero, were employed to study the physiological effects of acute maternal carbon monoxide intoxication upon the fetal rhesus monkey. 9 term pregnant female monkeys were exposed to 0.1 to 0.3% inspired CO over 1 to 3 hr. The mothers tolerated carboxyhemoglobin (COHb) levels exceeding 60% without clinical sequelae. The fetuses promptly developed profound hypoxia upon exposure of the mothers to CO. However, the fetal COHb levels rose only gradually over the 1 to 3 hr and thus contributed only slightly to the development of the early fetal hypoxia. Fetal hypoxia was associated with bradycardia, hypotension, and metabolic and, later, respiratory acidosis. A close correlation was noted between the severity of intrauterine hypoxia and the appearance of brain damage. Severe brain damage (brain swelling associated with hemorrhagic necrosis of the cerebral hemispheres) appeared only in those fetuses whose arterial O₂ content had fallen below 2.0 ml/100 ml for at least 45 min during the maternal CO intoxication.