The Preeclampsia Intervention Netherlands (PI-NL) trial is a double-blind, randomized placebo-controlled trial in 8 perinatal care hospitals with NICU in the Netherlands. The aim of the trial is to determine whether metformin can safely prolong pregnancy in patients with preterm preeclampsia (before 32 weeks of gestation), with or without HELLP syndrome, who do not require immediate delivery or termination of the pregnancy otherwise.