The purpose of this single arm, open label study will be to evaluate whether the dwell time of the epidural catheter, patients' position, the presence of active labor contractions and the priming volume of the epidural catheter may affect the sensitivity and specificity of CompuFlo to detect epidural pulse waveforms (EPW) to assess the correct placement of the catheter in the epidural space.

The purpose of this single arm, open label study will be to evaluate whether the dwell time of the epidural catheter, patients' position, the presence of active labor contractions and the priming volume of the epidural catheter may affect the sensitivity and specificity of CompuFlo to detect epidural pulse waveforms (EPW) to assess the correct placement of the catheter in the epidural space.

The primary objective will be the correlation between the appearance of EPW recorded by the CompuFlo and the correct placement of the epidural catheter as assessed by the occurrence of adequate bilateral labor analgesia.

Secondary objectives will be the effects of the dwell time of the epidural catheter, patients' position, the presence of active labor contractions and the priming volume of the epidural catheter on the EPW.

The study will enroll consecutive parturients in active labor who have received effective epidural labor analgesia with an epidural catheter. After epidural catheter priming, the occurrence or the absence of EPW will be investigated.

Endpoints (quantitative measurements required by the objectives)

Primary end points:

1. appearance and recording of EPW by using the CompuFlo instrument.
2. absence of EPW in case of inadequate analgesia, intravascular placement or unilateral analgesia 3) successful analgesia, defined as the occurrence of a visual analogue pain score less than 10/100 during the study period

Secondary end points:

• time from the last epidural bolus and the EPW recordings
• EPW recordings between uterine contractions and at the apex of a uterine contraction
• EPW recordings when the patient is supine or in left lateral decubitus
• EPW recordings during 10 sec Valsalva maneuver
• priming volume of saline necessary to detect EPW (5,10,15,20 ml)

Tertiary end points:

• epidural actual pressure (mmHg)
• EPW disappearance or absence during catheter removal or during ineffective analgesia

Inclusion Criteria:

• healthy women in active labor who received epidural analgesia

Exclusion Criteria:

• healthy women in active labor who received ineffective epidural analgesia

laboring women

healthy women in active labor who received epidural analgesia