The study is designed to compare the effectiveness of spinal anesthesia performed with fixed dose of hyperbaric bupivacaine regardless of patient's height and weight and anesthesia with the dose of bupivacaine that is adjusted to their height. Our clinical experience shows that spinal anesthesia using specific, relatively high dose of hyperbaric bupivacaine combined with opioid is very effective, regardless of parturient's weight and height, provides very good surgical conditions and assures patient's comfort while the rate of anesthesia - related complications is similar or less. Therefore, using height-adjusted protocols, although preferred in some centres, might not be necessary in order to provide good anaesthesia for cesarean delivery. Fixed dose regimen may have some additional advantages in obstetric anesthesia settings, as many of cesareans are performed out of hours, giving less room for mistakes in less experienced hands.

Two groups of parturients undergoing cesarean section are to be compared: anesthetized with fixed-dose regimen (intervention group) and anesthetized with height-adjusted dose regimen (control group). Patients are going to be randomized to one of the above groups, two anesthetists will be involved in anesthetic procedure: anesthetist that looks after the patient throughout the procedure will be blinded to the dose of anesthetic given intrathecally. Therefore his judgment of anesthetic effectiveness is not going to be biased and all patients will receive the same perioperative care in terms of fluid therapy, management of possible anesthesia - related complications and postoperative pain control.

Rate of effective spinal anesthetics, defined as adequate block level and no need for additional intraoperative analgesia has been established as primary outcome measure. Secondary outcome measures are rate of complications and amount of opioids used postoperatively. These are going to be statistically compared.

Inclusion Criteria:

• singleton pregnancy above 37Hbd scheduled for elective cesarean section
• ASA 1 or 2

Exclusion Criteria:

• absolute contraindications to spinal anesthesia
• delivery in progress
• non-singleton pregnancy
• BMI>35
• ultrasound - based estimation of fetal weight below 10 percentile
• pregnancy-induced hypertension
• more than 2 cesarean sections in patient's medical history
• significantly increased risk of obstetric hemorrhage (placenta previa)