The effects of paracervical block on uterine activity and beat-to-beat variability of the fetal heart rate.

Paracervical block analgesia with the use of lidocaine hydrochloride provoked little change in uterine activity. The general trend in uterine activity was an increase, although there was considerable variation in individual response. Beat-to-beat variability in the fetal heart rate increased following the block. The increase in variability began almost immediately, with the greatest increase occurring at a time when one would expect maximum maternal and fetal lidocaine levels. It is proposed that this increase in fetal heart rate variability is an early sign of post-paracervical block hypoxemia and/or hypoxia.