(nitroglycerine). Nitric oxide donors did not delay delivery or
improve neonatal outcome when compared to placebo, no
treatment or other tocolytics. Although, the side effect profile
was better than that with other tocolytics, more women
experienced headaches. It concluded that currently there is
insufficient evidence to support routine administration of nitric
oxide donors in the treatment of threatened preterm labor 55.
Maintenance of tocolysis
There is currently no evidence to support maintenance therapy
with tocolytic drugs. Terbutaline pump maintenance therapy
has not been shown to decrease the risk of preterm labor by
prolonging pregnancy 56. The benefits of maintenance therapy
with calcium channel blockers are still unclear 57, although it
has been reported that the gestational age and time gained
from initiation of maintenance therapy to delivery were longer
in women receiving oral maintenance tocolysis with nifedipine
58. There was however no decrease in the recurrence of
preterm labor episodes or improvement in the perinatal
outcome.
Corticosteroids
There is evidence that antenatal corticosteroids are associated
with a significant reducation in the rates of respiratory distress
syndrome, neonatal deaths and intraventricular hemorrhage,
although the numbers needed to treat increase significantly
after 34 weeks 59. The RCOG has recommended that antenatal
corticosteroids should be administered beween 24 and 34
weeks of gestation. Betamethasone appears to reduce the
incidence of necrotising enterocolitis as compared to
dexamethasone. The optimum treatment-delivery interval for
administration of antenatal corticosteroids is after 24 hours
and within 7 days of administration 59. A survey of UK
obstetricians conducted in 1997 reported that 98% of
responders prescribed repeated courses of antenatal
corticosteroids 60. One randomized controlled trial of single
versus multiple courses of corticosteroids involving 502
pregnant women between 24 and 32 weeks of gestation
concluded that weekly courses of antenatal corticosteriods
did not reduce composite neonatal morbidity compared to
single course of treatment 61. The RCOG guideline on antenatal
corticosteroids has concluded that currently there is no
evidence to recommend multiple courses of antenatal
corticosteriods 59. A recent 2 year follow up study after single
or multiple antenatal courses of corticosteroids found an
association of multiple courses of dexamethasone (not
betamethasone) with an increased risk of leukomalacia and 2
year infant neuro-developmental abnormalities 62.
Conclusion
Prevention and treatment of preterm labor is essential to
reduce adverse neonatal and infant outcome and to improve