Vitamin A and causes of maternal mortality: association and biological plausibility

Abstract

Objective: To review the association between major causes of maternal mortality and vitamin A, trying to determine if these associations are causal in nature, and to highlight possible biological pathways that may explain vitamin A effects. Design: Literature review, observational studies and clinical trials. The strength of association was determined by applying Bradford Hill criteria of causality. Results: In a vitamin A de®cient population, vitamin A is essential for adequate treatment of anaemia. While vitamin A does not seem to be capable of preventing uterine atony, obstetric or surgical trauma, which are important causes of haemorrhage, it might be capable of preventing or decreasing coagulopathy. Possible effects on the placenta as regards implantation, site and size are not clear. As regards pregnancy-related infections, vitamin A supplementation can improve wound healing by decreasing ®brosis and increasing transforming growth factor-b (TFG-b). It can increase resistance to infection by increasing mucosal integrity, increasing surface immunoglobulin A (sIgA) and enhancing adequate neutrophil function. If infection occurs, vitamin A can act as an immune enhancer, increasing the adequacy of natural killer (NK) cells and increasing antibody production. b-carotene in its provitamin form can act as an antioxidant by decreasing endothelial cell damage (the pathognomonic feature of pre-eclampsia) and promote the vasodilator effect of nitric oxide that might bring about a better outcome of toxaemia in pregnancy. It is unlikely that vitamin A or b-carotene has an effect on obstructed labour. Conclusions: Plausible biomedical pathways can only be constructed for obstetric haemorrhage, anaemia in pregnancy, hypertension in pregnancy and pregnancyrelated infections. A 40% reduction in the maternal mortality ratio, as observed in Nepal, is unlikely to be solely explained through the aforementioned pathways. KeywordsVitamin A Maternal mortality Biological plausibility Over the last decade, the role of vitamin A in decreasing the mortality and morbidity of infectious diseases in children has been established. Now, its importance to women of reproductive age has become a focus of interest. The results of a randomized controlled trial of vitamin A and b-carotene supplementation to women aged 15±45 years in Nepal suggest that this supplementation resulted in a signi®cant reduction in maternal mortality (vitamin A, 40% reduction; b-carotene, 50% reduction 1 ). Maternal mortality is a major public health problem in developing countries, and decreasing its burden is vital. Of the estimated 585 000 maternal deaths that occur every year approximately 25% are caused by haemorrhage, 15% by infections, 13% by abortion complications, 12% by complications of hypertensive disease in pregnancy, pre-eclampsia or eclampsia and 8% by obstructed labour 2 . Anaemic women are at higher risk of death if these complications occur.Only if the effect of vitamin A supplementation can be explained through biomedical pathways can we ass...

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