Preeclampsia is a major cause of maternal mortality. When preeclampsia presents prior to thirty-four weeks of gestation, expectant management is the standard practice in stable patients with the goal of extending pregnancy and therefore decreasing the risk of adverse outcomes in the premature neonate. Our aim was to assess the efficacy of Sildenafil, a phosphodiesterase inhibitor, versus placebo, in addition to expectant management, for the treatment of preterm preeclampsia to prolong pregnancy.