Sample size considerations: A sample size of 638 women in each treatment group will be required to detect a reduction in perinatal mortality from 9% to 5% or less in a treatment group using 80% power and a 5% significance level. With an expected loss to follow up of 10%, 2100 women are required. With a sample size of 2100 the study will be able to detect at least 75 g difference, i.e. a 2.5% change in birth weight.