Fetal Bradycardia after Paracervical Block

Abstract

Determinations of levels of a local anesthetic (mepivacaine) during labor after paracervical block indicated a rapid absorption of the drug into the maternal blood, with peak concentrations achieved by 10 to 20 minutes, followed by prompt placental passage to the fetus. The fetal bradycardia frequently encountered with this form of anesthesia appears to be related to high concentrations of the drug in fetal blood, 12.8 to 15 μg per milliliter. Although such levels might cause neonatal depression they do not appear to be high enough to cause death of a healthy fetus.