Clinical definitions
Preeclampsia with severe features was defined according to the ACOG criteria.1 Women were diagnosed with preeclampsia if they had new-onset elevated blood pressure (with systolic blood pressure greater than 140mmHg and/or diastolic blood pressure greater than 90mmHg on two occasions at least 4 hours apart) at or after 20 weeks of gestation or acute worsening of chronic blood pressure, with or without proteinuria (urinary excretion of 300mg protein/day). Severe features included systolic blood pressure greater than 160mmHg and/or diastolic blood pressure greater than 110mmHg, platelet count<100,000/ml, liver enzymes twice the normal concentration or symptoms of liver failure, right upper quadrant or epigastric pain, serum creatinine >1.1mg/dl, pulmonary edema, and/or new-onset cerebral or visual disturbances.
HELLP syndrome was defined by the clinical presentation of hemolysis, elevated liver enzymes, and low platelet count. We used the following criteria to make a diagnosis: lactate dehydrogenase (LDH) elevated to 600IU/L or more, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) elevated more than twice the upper limit of normal, and the platelets count less than 100,000 x 109/L.24
Birth weight was obtained immediately after birth using a standard electrical scale. Diagnosis of small for gestational age (SGA) was made using recorded birth weight and customized local nomograms25 and defined as birth weight less than the 10th percentile for gestational age and sex. Respiratory distress syndrome (RDS) was defined as the presence of clinical signs of respiratory distress (tachypnea, retractions, flaring, grunting, or cyanosis), with a requirement for supplemental oxygen with a fraction of inspired oxygen of more than 0.21 and a chest radiograph showing hypo-aeration and reticulogranular infiltrates. Respiratory support was characterized as continuous positive airway pressure (CPAP) or mechanical ventilation oxygen supplementation. Jaundice was defined as hyperbilirubinemia requiring treatment, and sepsis was confirmed by positive blood cultures. Hypoglycemia was defined as a glucose level of less than 40mg per deciliter at any time.
Statistical analysis
Continuous variables are presented as means and standard deviation or as median and inter-quartile range (IQR). Normality of the data was tested using the Shapiro-Wilk or Kolmogorov-Smirnov tests. Univariate comparison of continuous variables with normal distribution and dichotomous data or other continuous variables were performed with the use of student’s t test and Pearson correlation, respectively. Comparison between continuous variables not normally distributed was conducted with Mann–Whitney U test and Spearman’s rank correlation. Categorical variables are presented as numbers and percentages. The Pearson’s chi-square and Fisher’s exact tests were used for comparison of categorical variables. The significance threshold was set as p<0.05. Statistical analyses were conducted using the IBM Statistical Package for the Social Sciences (IBM SPSS for windows v.20; IBM Corporation Inc, Armonk, NY, USA).
The study protocol was approved by the Institutional Review Board at the Sheba Medical Center (9683-12-SMC), and written informed consent was obtained from all participants.