Because the majority of Caesarean deliveries are performed under neuraxial anaesthesia, Intrathecal morphine has become the gold standard for post-Caesarean delivery analgesia. However, postoperative nausea and vomiting (PONV) is the common side-effect of intrathecal morphine, affecting up to 60-80% of women without prophylaxis. PONV reduces maternal satisfaction and delays discharge from hospital, so it is important to prevent PONV in contemporary obstetric anaesthesia, particularly in the context of Enhanced Recovery After Surgery (ERAS) after Caesarean delivery.

According to the meta-analysis by Lizhong Wang et al., combined 5-HT3 antagonists plus dexamethasone are more effective than mono-therapy in preventing PONV associated with intrathecal morphine after Caesarean delivery. But, the role of prophylactic antiemetics in women receiving intrathecal morphine and lipophilic opioids is still unclear. As antiemetics were shown to be less effective in women receiving intrathecal morphine than in those receiving epidural morphine, Lizhong Wang et al., performed a further subgroup analysis based on whether intrathecal morphine was combined with lipophilic opioids or not. Surprisingly, the results in women who received intrathecal morphine alone were similar to those in the primary analyses; however, in those who received intrathecal morphine and lipophilic opioids, there were no statistical differences in almost all comparisons. This raises the question of whether the combination of intrathecal lipophilic opioids contributed to the reduced efficacy of antiemetics in women receiving intrathecal morphine The objective of the current study is to examine the effect of prophylactic use of combined 5-HT3 antagonists plus dexamethasone to decrease the incidence of postoperative nausea and vomiting in parturients undergoing CS under spinal anaesthesia who receive intrathecal morphine alone or combined with lipophilic opioids.

Because the majority of Caesarean deliveries are performed under neuraxial anaesthesia, Intrathecal morphine has become the gold standard for post-Caesarean delivery analgesia. However, postoperative nausea and vomiting (PONV) is the common side-effect of intrathecal morphine, affecting up to 60-80% of women without prophylaxis. PONV reduces maternal satisfaction and delays discharge from hospital, so it is important to prevent PONV in contemporary obstetric anaesthesia, particularly in the context of Enhanced Recovery After Surgery (ERAS) after Caesarean delivery.

According to the meta-analysis by Lizhong Wang et al., combined 5-HT3 antagonists plus dexamethasone are more effective than mono-therapy in preventing PONV associated with intrathecal morphine after Caesarean delivery. But, the role of prophylactic antiemetics in women receiving intrathecal morphine and lipophilic opioids is still unclear. As antiemetics were shown to be less effective in women receiving intrathecal morphine than in those receiving epidural morphine, Lizhong Wang et al., performed a further subgroup analysis based on whether intrathecal morphine was combined with lipophilic opioids or not. Surprisingly, the results in women who received intrathecal morphine alone were similar to those in the primary analyses; however, in those who received intrathecal morphine and lipophilic opioids, there were no statistical differences in almost all comparisons. This raises the question of whether the combination of intrathecal lipophilic opioids contributed to the reduced efficacy of antiemetics in women receiving intrathecal morphine

Inclusion Criteria:

• • Age from 19 to 40 years old.

  • Singleton pregnancies with a gestational age of at least 37 weeks.
  • pregnant women are scheduled for elective caesarean delivery.
  • Patients with stable vital signs.
  • Patients with normal laboratory investigations.
  • patients undergoing spinal anaesthesia for caesarean delivery via Pfannenstiel incision with exteriorization of the uterus

Exclusion Criteria:

• • Patient's refusal.

  • Age < 19 or > 40 years.
  • Height<150 cm, weight < 60 kg, body mass index (BMI) ≥40 kg/m2.
  • Contraindications to spinal anaesthesia (Coagulopathy, increased intracranial pressure, or local skin infection).
  • Patients with cardiac morbidities.
  • hypertensive disorders of pregnancy as pre-eclampsia.
  • peripartum bleeding.
  • Patients with respiratory morbidities.
  • Convulsions.
  • Bleeding diathesis.
  • Known allergy to any drugs used in this study.

Patients will be allocated in 1: 1 ratio into the two study groups using a web-based randomiser (https://www.randomizer.org/) to generate codes placed within sealed, opaque, sequentially numbered envelopes by a research assistant who will not be involved in patient care or assessment. This assistant also will prepare the study solutions in identical syringes that will be labelled ''study drug'' according to the assigned group