Inclusion Criteria:  18-45 years Primipara or multipara Singleton pregnancy ≥32 weeks American Society of Anesthesiologists physical status classification II to III Scheduled for cesarean section under spinal anesthesia  Exclusion Criteria:  Baseline blood pressure ≥180 mmHg Body height < 150 cm Body weight > 100 kg or body mass index (BMI) ≥ 40 kg/m2 Eclampsia or chronic hypertension Hemoglobin < 7g/dl Fetal distress, or known fetal developmental anomaly