The objective of our study is to determine the clinical utility related to the maintenance oral nifedipine therapy in patients with symptomatic placenta previa. This study is a prospective, randomized controlled trial with the inclusion, after 24 weeks gestation, of hospitalized patients with symptomatic placenta praevia. All patients may initially receive oral nifedipine therapy with steroid prophylaxis for 48 hours. After then, patients are randomly assigned to receive either oral nifedipine (20 mg every 8 hours) or placebo (one every 8 hours) until 37 weeks of gestation.

The primary outcome for the trial is the length of pregnancy in days after the enrollment. A sample size calculation is designed to detect at least a 14 -day difference in time gained in patients with maintenance oral nifedipine therapy. A sample size of about 52 patients per group would have a 80 % chance of detecting this difference at the 5 % level of significance.