Preterm birth is the most common and costly complication in obstetrics. It complicates up to
11% of all pregnancies and it is responsible for 70% of sick babies. The ideal way to stop
preterm labor when it occurs (which drug to use) is not known. Currently magnesium sulfate is
used by about 95% of all practitioners, but recent data suggest magnesium given this way may
be harmful for the baby's future development. Other drugs such as antiprostaglandin agents
are very effective in stopping uterine activity, but particularly when used for >48 hours
have been associated with both maternal and fetal sides effects. Lastly, calcium channel
antagonists are effective in stopping contractions and have very little in the way of
maternal and fetal side effects, but less data is available in the United States on their
use. Because there is no FDA approved drug to stop preterm labor, we purpose to randomize all
women with preterm labor (20-34 weeks) to receive one of the above three methods of stopping
preterm labor. The primary outcomes will be to see which agent stops the uterine contractions
most effectively, for the longest period of time with fewest relapses and results in
significant prolongation of pregnancy. If one of these agents is clearly superior to the
other two it would help women avoid early delivery or have significant extension of their
pregnancy to avoid some of the complications of preterm birth in the baby.