To determine whether prenatal corticosteroid therapy would reduce the incidence of
neonatal necrotizing enterocolitis (NEC), we assigned a total of 466 women admitted
in premature labor either to receive placebo (group A, n = 256), if delivery was expected
to occur within 24 hours of admission, or to receive betamethasone (group B, n = 210)
if delivery was expected to take place more than 24 hours after admission. All women
were free of severe medical complications or drug therapy; cases of intrauterine growth
retardation or premature rupture of the membranes were excluded. Their newborn infants,
excluding malformed, congenitally infected, and growth-retarded infants, were enrolled
in the study unless they had died before the age of 10 postnatal days. Babies born
to group A mothers (n = 248) were further assigned to a treatment group (group A1,
n = 130) receiving dexamethasone, 2 mg/kg/day by intravenous injection during the
first 7 days of life, or to a control group (group A2, n = 118) receiving 10% dextrose
solution placebo. Group B infants (prenatal betamethasone, n = 205) received neither
treatment nor placebo. The incidence of NEC in group A1 was 6.9% (9/130), and in group
A2 it was 14.4% (17/118) (p less than 0.05). In group B the incidence was 3.4% (7/205);
this was much lower than in group A2 (p less than 0.01) and lower than in group A
combined (10.4%) (p less than 0.01). There was no death from NEC and no surgical intervention
among group B patients. The mortality rate for group A1 (11%) was lower than for group
A2 (56%) (p less than 0.02). There were fewer indications for surgical intervention
for NEC in group A1 than in group A2. Histologic studies confirmed bowel ischemia
in all specimens analyzed. These data support the hypothesis that the incidence of
NEC is significantly reduced after prenatal steroid treatment. Although postnatal
therapy with steroids does not decrease the incidence as effectively as prenatal therapy,
it improves clinical outcome of NEC.