In the control group, a blood test to assess the sFlt-1/PlGF ratio will be performed, and the result will be concealed from investigators. As in current clinical practice, elective delivery will be scheduled at 37 weeks. If preeclampsia is first diagnosed after 37 weeks, immediate delivery will be recommended. If at any time after enrollment any of the following is present, immediate delivery (within 24 hours) will be recommended: preeclampsia with severe features according to ACOG criteria, decreased fetal movements, absent or reversed diastolic flow in the umbilical artery, non-reassuring CTG, biophysical profile score ≤6, or oligohydramnios.

If sFlt-1/PlGF <38, expectant management will be followed until 39 weeks. If any other medical condition is present, local protocols for the specific condition will be followed. If fetal growth restriction in present (with antegrade diastolic umbilical flow), weekly repetition of sFlt-1/PlGF wil be done. If sFlt-1/PlGF ≥38, delivery at 37 weeks will be recommended, or immediate delivery if the patient is enrolled after 37 weeks. If at any time after enrollment any of the following is present, immediate delivery (within 24 hours) will be recommended: preeclampsia with severe features according to ACOG criteria, decreased fetal movements, absent or reversed diastolic flow in the umbilical artery, non-reassuring CTG, biophysical profile score ≤6, sFlt-1/PlGF ≥38 or oligohydramnios.

If the angiogenic factors are normal (sFlt-1/PlGF <38), expectant management will be followed until 39 weeks, instead of delivery at ≥37 weeks of gestation as in standard care for preeclampsia without severe features.

The primary outcome is a composite poor maternal outcome, defined as maternal mortality, severe maternal morbidity (eclampsia, HELLP syndrome, thromboembolic disease, pulmonary edema, or placental abruption), preeclampsia with severe features, and major postpartum hemorrhage (>1000 mL).

Neonatal morbidity is defined as the occurrence of at least one of the following: 5-minute Apgar score <7, NICU admission, fetal death, neonatal death, sepsis, hypoglycemia, transient tachypnea of the newborn, respiratory distress syndrome, meconium aspiration syndrome, periventricular leukomalacia, intraventricular hemorrhage, seizures, necrotizing enterocolitis, neonatal jaundice requiring phototherapy, neonatal birthweight <2500 g, or elective early-term delivery (37+0-38+6 weeks of gestation).