Primary outcome: Compare the duration of analgesia. Secondary outcome: analgesic potency of bupivacaine and fentanyl versus levobupivacaine and fentanyl.

The pain of childbirth is the most severe pain any women can endure in their life time. Painful uterine contractions lead to maternal hyperventilation and increased catecholamine concentrations resulting im maternal and fetal hypoxemia.

Labour pain when unrelieved can have adverse effect on the course of labour as well as on the fetal wellbeing. An effective labour analgesia lead to better fetal and maternal outcome.

Although the gold standard in labour analgesia is utilization of epidural services which are widely used to provide pain-free labour in many parts of the world and and have the advantage of providing flexibility to meet the needs of each patient . Epidurals have long been associated with increased oxytocin use, increased fetal malposition, increased rates of instrumental and cesarian delivery, and longer labour .

The use of single-shot intrathecal low dose found to be effective . The advantages of this form of technique include the rapidity of onset and reliability, with minimal hemodynamic changes and motor block. Spinal block is cheaper as well as less technically challenging when compared to epidural and combined spinal epidural block. Intrathecal analgesia alone is useful when duration of labour can be reasonably estimated. Opioid combined with a small dose of local anesthetic provides rapid analgesia and dissipates when no longer needed.

Bupivacaine because of its least placental transfer, due to high protein binding and minimal motor block compared to sensory block in lower doses, has become the popular choice for labor analgesia. Addition of neuraxial lipid soluble opioids permitted reduction in the dose while maintaining effective analgesia and minimizing potential adverse effects on the progress of labor and lower extremity motor block .

Levobupivacaine is the S (-) enantiomer of racemic bupivacaine. Previous studies have shown that it exhibits a clinical profile similar to bupivacaine with the added advantage of less motor impairment .

Inclusion Criteria:

1. singleton pregnancies
2. vertex presentation who will be in the active phase of labour with a cervical dilatation >4cm
3. normal fetal heart rate.

Exclusion Criteria:

• 1-Parturients with systemic diseases 2-Suspected cesarian section which include, in order of frequency, labor dystocia, abnormal or indeterminate (formerly, nonreassuring) fetal heart rate tracing, fetal malpresentation, multiple gestation, and suspected fetal macrosomia.
• 3 Fetus with known or suspected congenital abnormalities, and 4-Administration of parentral or oral analgesics before initiation of neuraxial analgesia will be excluded from the study.