CYP2D6 and psychiatric disorder: Higher opioid consumption (>70 MME) showed a trend toward an increased risk of maternal PONV (adjusted RR = 2.56; 95%CI: 0.70–9.29; p = 0.36), after accounting for total opioid consumptions, CYP2D6 phenotype, average pain score over three postpartum days, age, race, BMI, and any mental illness.