Efficacy of Oral Nifedipine Versus Labetalol in the Emergency Management of Hypertensive Crisis in Pregnancy: A Systematic Review of Randomized Controlled Trials and Primary Studies

Introduction: Hypertensive disorders complicate one in ten pregnancies and remain leading causes of maternal mortality worldwide. Severe hypertension (SBP ≥160 mmHg and/or DBP ≥110 mmHg) constitutes an obstetric emergency due to imminent risks of intracerebral hemorrhage, eclampsia, pulmonary edema, and placental abruption. Oral nifedipine and labetalol are the most widely used first-line agents, yet comparative evidence remains fragmented. This review aimed to determine whether oral nifedipine differs from labetalol in acute control of hypertensive crisis in pregnancy across fifteen pre-specified clinical outcomes. Methods: A systematic review was conducted per PRISMA 2020 guidelines. Eligible designs included RCTs, quasi-experimental trials, prospective/retrospective cohorts, case-control, and cross-sectional studies comparing nifedipine with labetalol in pregnant women with severe hypertension. Risk of bias was appraised with Cochrane RoB 2 and ROBINS-I; certainty with GRADE. A binormal ROC reconstruction was performed for time-to-target blood pressure, with AUC representing probability of earlier attainment. Results: Twenty-one primary studies (15 RCTs, 1 quasi-experimental, 2 prospective cohorts, 3 retrospective cohorts) comprising ≥9,889 pregnant women from ten countries were included. Oral nifedipine reached target BP significantly faster than labetalol: pooled MD -9.10 minutes (95% CI -13.69 to -4.51; τ²=11.55; I²=44.2%). Reconstructed pooled AUC was 0.668 (95% CI 0.609-0.727; I²=0.0%), significantly exceeding 0.500. Nifedipine required fewer doses, produced greater systolic/diastolic reduction, and increased urine output. Maternal/perinatal adverse events, caesarean delivery, fetal heart-rate abnormality, Apgar<7, and NICU admission did not differ significantly. One large observational cohort favored labetalol for composite maternal morbidity (aRR 1.33, 95% CI 1.07-1.64). Risk of bias was low in 5/15 RCTs, moderate-to-serious in all non-randomized studies. GRADE certainty was moderate for time-to-target and dose requirement, low/very low for patient-important outcomes. Discussion: Nifedipine's pharmacodynamic superiority in speed and dose economy is consistent, mechanistically coherent, and reproducible. However, speed is a surrogate outcome; the largest observational dataset raises signals of increased eclampsia, HELLP, and renal failure with nifedipine. The AUC of 0.668 quantifies the advantage as modest—statistically significant but far from the >0.80 threshold justifying categorical protocol change. Conclusion: Oral nifedipine controls hypertensive crisis significantly faster with fewer doses than labetalol, with a moderate discriminative advantage (AUC 0.668) and equivalent maternal/perinatal safety in randomized evidence. Requiring no IV access, infusion pump, or continuous cardiotocography, nifedipine should be regarded as a legitimate first-line option—and in resource-constrained settings, the preferred option.