Fetal blood-gas values during fetoscopic myelomeningocele repair performed under carbon dioxide insufflation

Fetoscopic myelomeningocele (MMC) repair is performed using intrauterine carbon dioxide (CO₂) insufflation. Sheep experiments have shown that CO₂ insufflation is associated with significant fetal acidemia; however, corresponding data for human pregnancy are not available. We performed umbilical venous cord blood sampling in three patients during fetoscopic MMC repair at 25 + 1, 25 + 3 and 24 + 0 weeks' gestation, respectively. Fetal venous pH at the beginning of CO₂ insufflation was 7.36, 7.46 and 7.37, respectively in the three fetuses, and repeat values were 7.28, 7.35 and 7.36 after 181, 159 and 149 min, respectively. The partial pressure of oxygen and CO₂ was maintained in the normal range during these times, and pH decrease was less in Patient 3 who received humidified CO₂ insufflation. Our observations suggest that, in contrast to sheep experiments, CO₂ insufflation during fetoscopic myelomeningocele repair does not cause acidemia in human fetuses.