Diagnostic criteria
Pre-eclampsia was diagnosed according to the American College of Obstetricians and Gynecologists (ACOG) definition (13). Hypertension was defined as blood pressure ≥ 140/90 mmHg on two separate occasions (≥ 24 hours apart). The proteinuria definition used was either ≥ 300 mg of protein per 24-hour urine collection or a protein/creatinine ratio ≥ 30 mg/mmol. Note that 2+ protein or greater in dipstick urinalysis and ≥ 30 mg of protein/dl in a spot urine sample were not considered suitable markers of proteinuria. In the absence of proteinuria, preeclampsia was defined as new onset of hypertension with the new onset of any of the following: thrombocytopenia (< 100,000/μl), kidney failure (creatinine concentration > 1.1 mg/dl), impaired liver function, pulmonary edema or cerebral or visual symptoms.
Final outcomes were reviewed by an independent obstetrician and assessed at time of delivery. To be considered early-onset pre-eclampsia, the onset had to occur before 34 weeks of pregnancy (2).
Intrauterine growth restriction is defined as an estimated fetal weight below the 10th percentile due to a pathological process that inhibits normal growth potential. This pathological process must be demonstrated after 22 weeks of gestation by oligohydramnios (amniotic fluid index below the 10th percentile) or a Doppler ultrasound of the umbilical artery with a pulsatility index above the 95th percentile.