There is increasing evidence that fetal exposure to macro- and micronutrient undernutrition is linked to a higher metabolic and cardiovascular disease risk in adult life. This process has been termed “fetal programming”. Human data concerning the effects of at various stages of pregnancy have been gleaned from retrospective epidemiological studies. Adult offspring of survivors of the Dutch famine of 1945 had an increased risk of impaired glucose tolerance and developing type 2 diabetes if their exposure to poor nutrition in the womb was in late gestation and an increased risk of coronary heart disease and dyslipidaemia if the exposure was early in gestation (1, 2). A retrospective study from The Gambia has linked exposure of unborn life to the “hungry season” with a higher rate of death due to infectious causes in early adulthood. This would increase the possibility that maternal undernutrition during pregnancy affects their offspring’s immune functions (3). Other studies have failed to confirm these findings (4).
Substantial literature is available regarding the association between folate deficiency in pregnancy and increased risk of premature delivery, low birth weight and neural tube defects (5). In a subgroup of the population, this may be because of an interaction between low folate status and genetic traits, such as variations (polymorphisms) in the methylenetetrahydrofolate reductase gene, which result in increased blood homocysteine levels when folate intake is low (6). High homocysteine concentrations in pregnancy are associated with adverse pregnancy outcomes and hypertensive disorders that can affect fetal growth (7, 8).
Gene expression, impacting cell differentiation and the development of organs can be regulated by mechanisms other than changes in the underlying DNA sequence, namely by so called ’epigenetic’ changes, such as ‘DNA methylation’ or ‘histone deacetylation’. Among the environmental conditions influencing gene expression, nutrition is one of the most important epigenetic factors. DNA methylation, for example, seems to depend on the availability of vitamins B6 as well as vitamin B12 and folate (9).
Vitamin B12 deficiency is also associated with high homocysteine concentrations (10), suggesting that low vitamin B12 status in pregnancy may also be a risk factor for neural tube defects (11). Since high homocysteine concentrations are themselves associated with an increased risk of cardiovascular disease, the link between low birth weight and later cardiovascular disease at a population level may be at least in part mediated via genetic variations in folate and B12 metabolism.
Acting through its specific receptor, vitamin D can produce various biological effects on human health via genomic, non-genomic or hormonal mechanisms. Vitamin D deficiency in pregnant women is potentially associated with increased risk of preeclampsia, insulin resistance and gestational diabetes mellitus. In addition, experimental data also anticipate that vitamin D sufficiency is critical for fetal development, particularly for the brain and immunological functions. Thus, vitamin D deficiency during pregnancy may not only interfere with maternal skeletal preservation and fetal skeletal formation, but may also have an impact on fetal ‘imprinting’ that could affect chronic disease susceptibility soon after birth and later in life (12).
Other data have shown that maternal Vitamin D supplementation during pregnancy was associated with an increase in the gene expression, raising the levels of so-called ‘immunoglobuline-like transcipts’ in cord blood. This finding may point towards an early induction of immunological tolerance in the fetus by maternal vitamin D intake (13). The vitamin D receptor (VDR) seems to play an important role in several immune functions, e.g. by modulating T cell differentiation (14). Genetic variations of VDR are associated with immune-related diseases such as asthma.
In epidemiologic studies of children and adults, several groups have reported associations between asthma and reduced intake and blood levels of dietary nutrients such as antioxidant vitamins C and E, as well as beta-carotene, selenium and zinc (15). However, supplementation with those antioxidants has not been consistently associated with improved asthma outcomes (16, 17). One possible explanation for the inconsistencies between epidemiologic and intervention studies is that dietary antioxidants primarily influence the development of asthma during a critical time period early in life. Studies have shown that low maternal vitamin E intake during pregnancy is associated with increased likelihood of wheezing and asthma in 5-year-old children (18). More recent findings support the concept of early fetal programming of respiratory disease. According to those, maternal vitamin E status may be one determinant for growth of the fetus and fetal lungs during early pregnancy (19).
Essential fatty acids
Research is investigating the complex roles of dietary fatty acids in regulating gene expression and intracellular communication. Accumulating evidence supports the hypothesis that maternal intakes of the omega-3 fatty acids docosanexaenic acid (DHA) and eicosapentaenic acid (EPA), as well as omega-6 fatty acids in gestation and lactation (maybe involving excess Omega-6 and inadequate Omega-3 fatty acids), can have an impact on the developing infant tissue lipids and metabolic pathways of cells that receive neuronal input. Further research in the field of metabolic programming is required to understand the need for different omega-3 and omega-6 fatty acids during fetal and infant life, as well as their roles with respect to development of energy balance and neurometabolism (20). One initial study indicates beneficial long-term neurophysiologic and neurobehavioral effects of adequate omega-3 fatty acid intakes during pregnancy on memory function in school-age children (21).
A trial of maternal calcium supplementation has shown that blood pressure is lower in the 7-year-old offspring of calcium-supplemented mothers (22). A prospective cohort study has also found a strong association between low infant blood pressure at 6 months and the calcium intake that their mothers received via supplements (23).
Low iron status in pregnant women was found to be related to increased placental size (24). The significance of this upon the offspring’s later health is unknown, but an association between increased placental size and increased blood pressure in the offspring has been noted in epidemiological studies (25). A randomized double-blind clinical trial measuring iron levels with or without multi-micronutrient supplementation in pregnant women has shown no additional effect on birth weight from micronutrients over iron supplements alone (26).