Approximately 1000 women die from complications related to pregnancy or childbirth worldwide every day (1). Almost all of these deaths occur in developing countries, and most could be averted by preventing complications such as severe bleeding (haemorrhage), infections and high blood pressure, and diseases such as malaria, anaemia and human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) during pregnancy and postpartum (2). Neonatal deaths account for 36% of deaths among children under 5 years of age worldwide (3, 4). These deaths are mainly due to prematurity and low birth weight (31%), neonatal infections (26%), birth asphyxia (lack of oxygen at birth) and birth trauma (23%). A non-negligible proportion of neonates die because of congenital anomalies (6.8%), other non-infectious perinatal causes (5.7%), tetanus (5%) and diarrhoeal diseases (2.6%).

Vitamin A deficiency also remains a public health problem among women and children, affecting an estimated 190 million preschool-age children and 19 million pregnant women (5), with the highest burden found in the World Health Organization (WHO) regions of Africa and South-East Asia. During lactation, vitamin A is essential for maternal health and vision (6). The recommended nutrient intake of vitamin A for postpartum women is 850 μg retinol equivalents (RE)/day (7), which may be difficult to achieve through the diet alone in some areas. Dietary sources of provitamin A include vegetables such as carrot, pumpkin, papaya and red palm oil; animal foods rich in preformed vitamin A include dairy products (whole milk, yogurt, cheese), liver, fish oils and human milk (6, 7).

Infants are usually born with low body stores of vitamin A. Breast milk of well-nourished mothers is rich in vitamin A and is its best source for the infant (8). Therefore, mothers are encouraged to exclusively breastfeed for the first 6 months postpartum. The concentration of vitamin A in breast milk is highest in the first 21 days postpartum, that is, in the colostrum in the first 4–6 days and in the transitional milk in the next 7–21 days (9). Following this, in industrialized countries, the concentration of vitamin A usually remains stable during the remainder of lactation (10).

In areas where vitamin A deficiency is common, mothers may produce breast milk with lower concentrations of vitamin A (9). However, if a mother cannot meet the increased vitamin A requirements during lactation through the diet, her body will attempt to compensate for the low levels of vitamin A in the breast milk by drawing on the vitamin A reserves in the liver (11). Vitamin A plays an important role in vision, growth and physical development, and immune function, and deficiency of vitamin A increases the risk of night blindness and other ocular conditions such as xerophthalmia (12), especially during times when infectious disease rates are high and/or during seasons when food sources rich in vitamin A are scarce (13).

Maternal dietary intake is an important determinant of breast milk vitamin A concentrations and an infant's vitamin A status (9, 14). Programmes such as postpartum supplementation, dietary diversification and food fortification with vitamin A have been used to improve women's vitamin A status and to increase the vitamin A content of breast milk (15). This protects the vitamin A reserves of lactating women while addressing the problem of low intakes of vitamin A from breast milk in infants (16).

Vitamin A supplements are mostly well tolerated by postpartum women (17); however, maternal supplementation with high doses (more than 50 000 IU) can have side-effects such as nausea, headache, fever, vomiting, increased cerebrospinal fluid pressure, blurred vision, drowsiness and lack of muscle coordination (18). However, these symptoms are generally transient with no long-term adverse effects (19).