Tamura T, et al. - One-hundred-and-seventy-six pregnant women scheduled for elective cesarean section with spinal anesthesia were recruited by the researchers in order to contrast the postoperative analgesic effects of ultrasound-guided posterior quadratus lumborum block with spinal morphine, post-cesarean section, using the visual analogue scale. Patients were randomized into 4 groups (spinal morphine 0.1 mg {group M⁺}; spinal saline {M^-}; posterior quadratus lumborum block using either 0.3% ropivacaine [0.45 mL/kg each side, maximum 150 mg] {group pQ⁺}; or saline {group pQ^-}). At 0.5, 1, 2, 4, 6, 18 and 24 h post-surgery, postoperative pain was studied. Markedly different pain scores 6 h after surgery, both at rest and when moving were observed when M⁺pQ⁺ group with the M-pQ⁺ or M^-pQ^- groups and M⁺pQ^- group with the M^- pQ⁺ or M^- pQ^- groups were compared. However, no difference between the M⁺pQ⁺ and M⁺pQ^- groups, or between the M^-pQ⁺ and M^-pQ^- groups could be recognized. Hence, improvement in postoperative analgesia via spinal morphine was concluded, however, no improvement through the combination of posterior quadratus lumborum block with spinal morphine could be recognized.