A healthy, balanced diet is strongly recommended before, during, and after pregnancy. Good nutrition and appropriate weight gain can improve pregnancy outcomes.
Although, in the general population, a healthy balanced diet should largely obviate the need for vitamin and mineral supplementation, pregnancy, and lactation create extra nutritional demands that, for some individuals, may make supplementation advisable.
A prophylactic dose of 300μg (0.3mg) per day throughout pregnancy was suggested in 1968 by the World Health Organization (WHO). The supplemental dose was increased to 400μg (0.4mg) of folic acid per day in 1998 following publication of several studies supporting the periconceptional use of this nutrient in the prevention of neural tube defects. This dose was deemed to provide more folic acid than required to produce an optimal haemoglobin response in pregnant women.
VITAMIN D SUPPLEMENTATION IN PREGNANT WOMEN
Vitamin D deficiency is thought to be common among pregnant women, particularly during the winter months, and has been found to be associated with an increased risk of pre-eclampsia, gestational diabetes mellitus, preterm birth, and other tissue specific conditions.
The largest source of vitamin D in adults is synthesis from solar radiation; half an hour of sunlight delivers 50 000 iu of vitamin D with white complexioned skin. Dietary intake of vitamin D makes a relatively small contribution to overall vitamin D status as there is little vitamin D that occurs naturally in the food supply. Melanin absorbs ultraviolet B (UVB) from sunlight and diminishes cholecalciferol production by at least 90%. Dietary vitamin D is absorbed from the intestine and circulates in plasma bound to a vitamin D binding protein.
Pre-eclampsia and neonatal hypocalcaemia are the most prevalent complications of maternal hypocalcaemia and are clearly associated with substantial morbidity.
A statistical association of glucose intolerance and hypovitaminosis D has been demonstrated. Maternal vitamin D is important to foetal bone development. Foetal lung development and neonatal immune conditions such as asthma may relate in part to maternal vitamin D levels.
The nutritional status of women when becoming pregnant and during pregnancy can have significant influence on foetal, infant, and maternal health outcomes.
Micronutrient deficiencies such as calcium, iron, vitamin A, and iodine can lead to poor maternal health outcomes and pregnancy complications which put the mother and baby at risk. Poor maternal weight gain in pregnancy due to an inadequate diet increases the risk of premature delivery, low birthweight and birth defects.
Optimisation of foetal development requires the achievement of adequate nutritional status of the mother prior to conception. Interventions to reduce chronic disease risk in future generations should address dietary and lifestyle change in infancy and adolescence, to ensure adequate nutrition throughout adolescent and reproductive years and in order to improve women’s reproductive health.
- Efforts to improve diet quality will need to address health inequalities and consider the diet as a whole without neglecting the importance of supplementation with folic acid and vitamin D. Existing advice to increase fruit and vegetable consumption is designed to improve the overall micronutrient status of women along with appropriate folic acid and vitamin D supplementation.
- It is particularly important that adolescent and young adult women achieve a body composition and metabolic capacity capable of meeting the stresses of pregnancy as well as their own requirements. This will help to address the health and economic implications of the rising prevalence of maternal obesity for future generations.
- There is a need to increase appreciation of the reproductive risks associated with excess maternal body weight and to support women in achieving and maintaining a healthy weight in preparation for pregnancy.
- The increased nutritional vulnerability of underweight women needs to be addressed. There is also a need to recognise the increased nutrient demands on adolescent and young women who become pregnant before completing their own growth.
- Strategies that promote, protect, and support exclusive breastfeeding for around the first six months of an infant’s life should be enhanced, and should recognise the benefits for long-term health.
- The greatest impact is likely to be achieved by intervening in the early postnatal weeks, when the rate of discontinuation is greatest.
- In populations where calcium intake is low, calcium supplementation as part of the antenatal care is recommended for the prevention of pre-eclampsia in pregnant women, particularly among those at higher risk of developing hypertension (strong recommendation).