Most living organisms have developed well-integrated, antioxidant defenses to scavenge free radicals and control their intracellular concentration. A loss of balance between free radicals and antioxidants (the redox balance) is one mechanism of cell injury in diseases associated with inflammation. N-acetylcysteine is an approved anti-oxidant medication drug used during pregnancy for treatment of mothers with acetaminophen (Tylenol) toxicity. N-acetylcysteine has been safely administered during pregnancy in over 100 women who overdosed with Tylenol and to preterm and healthy term newborns for other purposes. It is a goal of our trial to prevent free radical formation by administering N-acetylcysteine and to further study whether the outcome of preterm deliveries will improve compared to a control group which will not receive placebo infusion