Background. Undernutrition causes over 3.5 million child deaths a year, with vitamin A deficiency alone responsible for almost 0.6 million child deaths per year1. Vitamin A supplementation of children above 6 months of age has been shown to reduce overall mortality by 23%. The effect of vitamin A supplementation in newborns on morbidity and mortality is less clear, with three studies in India, Indonesia and Nepal showing reductions in neonatal mortality of 22%, 64% and 15% respectively, but with 2 other trials in Africa reporting no effect. In view of the expected health benefits of improved vitamin A status of infants, WHO currently recommends that women should receive a high dose (200.000 IU ) of vitamin A within the first 6 weeks postpartum, in order to improve maternal vitamin A status, the vitamin A content of breast milk, and thereby the vitamin A status of their infants. However, several recent trials in which women received 200.000 IU vitamin A directly post-partum, reported no improvement in vitamin A status of either mother or her infant at 6 mo of age, not even after doubling the dose to 400.000 IU. In these studies vitamin A was given within a week of delivery, the current typical practice even though WHO actually states a window of 6 weeks after delivery. In contrast, 2 earlier studies in Bangladesh and Indonesia reported a large impact of post-partum maternal supplementation on vitamin A status in infants at 6 mo of age. In these studies, women received a high dose vitamin A supplement not directly post-partum, but somewhere in the first 6 weeks after delivery. The WHO recommendation on maternal post-partum vitamin A supplementation was based on the effects observed in these earlier studies, but the more recent studies suggest now that this intervention is not effective, and that millions of women are receiving a high dose vitamin A supplement without clear benefits for vitamin A status of either the women or their children. The difference in timing between the earlier studies and the recent studies of giving the vitamin A may hold the key, and we believe we have identified the biological reason why timing of the supplementation could be of the utmost importance: the inflammatory response to delivery.