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.