Effects on the Fetus of General Versus Regional Anesthesia

General anesthesia for cesarean delivery may cause direct neonatal respiratory depression caused by placental transfer of drugs at therapeutic maternal plasma drug concentrations. The predominant adverse effect of regional and particularly spinal anesthesia is indirect reduction of uteroplacental blood flow as a result of sympatholysis and maternal hypoperfusion. When properly conducted, both techniques are associated with such a low incidence of serious adverse neonatal outcome that controlled trials are unable to identify anesthetic choices as independent risk factors. When comparing the effects on less serious adverse outcomes, general anesthesia may be associated with a lower 1-min and occasionally with a lower 5-min Apgar score; it may also be associated with a greater need for neonatal resuscitation, but these events are rare in all anesthetic groups. On the other hand, spinal anesthesia is associated with a lower umbilical artery pH and base excess; although this may be related to the use of ephedrine. Epidural anesthesia emerges best from these two comparisons, but a higher incidence of patchy anesthesia may result in increased need for sedation or general anesthesia with direct fetal respiratory depression. While regional anesthesia is preferred for cesarean delivery whenever possible, the choice should be determined by the presence of risk factors and patient preference.