This double-masked, placebo-controlled trial of 10,000 subjects is designed to evaluate the effects of antioxidant therapy in preventing serious complications associated with pregnancy-related hypertension in low risk, nulliparous women who begin treatment at 9-16 weeks gestation. The hypothesis being tested is that antioxidant therapy initiated prior to 16 weeks gestation will reduce the frequency of serious maternal and infant complications associated with pregnancy-related hypertension.