Micronutrient supplementation in pregnancy in developing countriesBMJ 2008; 337 doi: https://doi.org/10.1136/bmj.a1942 (Published 07 November 2008) Cite this as: BMJ 2008;337:a1942
Maternal undernutrition before and during pregnancy is linked to poor pregnancy outcomes. Maternal micronutritional deficiency can jeopardise the intrauterine growth or development of the fetus and increase perinatal morbidity and mortality by disrupting protein metabolism, gene transcription, endocrine functions, and transport of nutrients.1
About 20% and 50% of women in south Asia and sub-Saharan Africa, respectively, have low body mass index (<18.5), a known risk factor for poor pregnancy outcomes.2 During pregnancy, 50-70% of women in developing countries have anaemia and night blindness, a sign of vitamin A deficiency.3 In the linked randomised controlled trial (doi:10.1136/bmj.a2001), Zeng and colleagues compare the effect of antenatal supplementation with multiple micronutrients, iron and folic acid, or folic acid alone on birth weight, duration of gestation, and maternal haemoglobin in the third trimester.4
Politics, social class, social milieu, cultural practices, access to and use of health care (including perinatal care), and dietary practices are key determinants of maternal malnutrition and poor perinatal survival.5 Clearly, even with renewed interest it might take years to implement well informed policies that would have a sustainable effect on these determinants. In most settings increasing dietary energy intake or providing additional micronutrients (either as supplements or by fortifying local foods) is the best way to improve the nutritional status of women.6 7 The beneficial effects of vitamin A, iodine, folic acid, and iron supplementation on the outcomes of pregnancy and the health of the newborn, or both, has been well documented in most populations.
The World Health Organization advocates the routine use of iron-folic acid supplements in antenatal care, and most governments strive to implement this policy. Lately, interest has focused on the effects of multiple micronutrient supplements on pregnancy and birth outcomes in areas where deficiency of multiple micronutrients is prevalent.8 A meta-analysis of nine high quality studies including 15 378 women living in low income countries found that, although multiple micronutrient supplements significantly decreased the risk of infants having low birth weight, being small for gestational age, and having anaemia when compared with no supplements, placebo supplements, and supplements of only one or two micronutrients, they provided no additional benefits over iron-folic acid supplements.9
Zeng and colleagues evaluated the effect of daily supplements of iron-folic acid (60 mg of iron, 400 µg folic acid) or a combination of 15 multiple micronutrients (with 30 mg of iron, as recommended by Unicef) on maternal anaemia, duration of gestation, birth weight, neonatal mortality, and perinatal mortality in rural China. The comparison arm consisted of women randomly allocated to receive folic acid supplements, the only antenatal supplement promoted by the Ministry of China to prevent neural tube defects. The current antenatal care policy in China gave the authors a unique opportunity to study the effects of iron supplementation on pregnancy and birth outcomes. Moreover, pregnant women randomly allocated to two intervention groups received 60 mg/day or 30 mg/day of iron, which enabled the authors to evaluate any possible dose dependent effects of iron supplementation on the outcomes of interest. Iron-folic acid supplementation significantly reduced the risk of early preterm delivery (<34 weeks), and early neonatal mortality compared with folic acid alone (relative risk 0.50, 95% confidence interval 0.27 to 0.94). Although supplementation with multiple micronutrients significantly increased the birth weight compared with folic acid (42 g, 7 g to 78 g), this did not translate into a significant reduction in early neonatal mortality. Both micronutrients and iron-folic acid significantly increased gestational age at birth and haemoglobin concentrations compared with folic acid alone, but nearly half of the women taking micronutrients and iron-folic acid remained anaemic in the third trimester.
Micronutritional interventions clearly have a major role in improving women’s health, pregnancy, birth outcomes, and child survival. Future endeavours must focus on carefully designed nutritional research that could help elucidate the mechanisms by which micronutrients exert beneficial effects and increase our understanding of the interactions between micronutrients that influence their bioavailability. Prospective high quality community trials should look at the influence of maternal nutritional status on pregnancy and perinatal outcomes. They should also focus on identifying the optimal micronutritional approach (supplementation with single or multiple micronutrients) in representative populations and inform local policies. In due course, the effectiveness of these approaches should be tested at the community level. Ultimately, long term efforts should involve a multidimensional approach to bring about a global improvement in women’s health, precipitate social changes, and bridge cultural gaps.
Cite this as: BMJ 2008;337:a1942
Competing interests: None declared.
Provenance and peer review: Commissioned; not externally peer reviewed.