We conducted the trial from July 2003 through
February 2008 at the 16 clinical centers and the
independent data coordinating center of the MFMU
Network. Pregnant women who had a singleton
fetus with a gestational age of less than 16 weeks
0 days at the time of screening were eligible for
inclusion in the study. Gestational age at randomization
was between 9 weeks 0 days and 16 weeks
6 days. Women were eligible for inclusion if they
had not had a previous pregnancy that lasted beyond
19 weeks 6 days. Gestational age was determined
before randomization with the use of a
previously described algorithm15 that took into
account the date of the last menstrual period (if
reliable information was available) and results of
the earliest ultrasound examination. Women were
not eligible if they had elevated systolic blood
pressure (135 mm Hg or higher), elevated diastolic
blood pressure (85 mm Hg or higher), or proteinuria
(300 mg of protein or more, as measured
in a 24-hour urine sample, or a urine-dipstick result
of 1+ or higher for protein), were taking or had
taken antihypertensive medication, or were taking
more than 150 mg of vitamin C or more than
75 IU of vitamin E daily. Other exclusion criteria
were diabetes that was present before the pregnancy,
treatment with antiplatelet drugs or nonsteroidal
antiinflammatory agents, uterine bleeding
within the week before recruitment, uterine
malformation, serious medical condition, known
fetal anomaly or aneuploidy, in vitro fertilization
resulting in the current pregnancy, or abuse of
illicit drugs or alcohol.