Folate status and pregnancy outcome

Methylenetetrahydrofolate reductase C677T polymorphism and pregnancy complications

OBJECTIVE

To investigate the frequency of the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism in women with intrauterine fetal death, preeclampsia, preterm delivery, and small for gestational age (SGA) infants.

METHODS

In a prospective cohort study, DNA from 2,000 pregnant women were analyzed for MTHFR C677T by DNA microarray (wild-type allele, C; mutant allele, T).

RESULTS

One thousand six hundred seventy-five women completed the study. Of these, 16.6% (278 women with 556 genetic alleles) developed at least one pregnancy complication and were designated study cases. There were 1,397 women (with 2,794 genetic alleles) who served as controls. MTHFR C677T allele frequencies were significantly different between cases and controls (C [wild-type]: 346 of 556 [62%]; T [mutant]: 210 of 556 [38%] compared with C: 1,911 of 2,794 [68%]; T: 883 of 2,794 [32%]; P=.005; odds ratio [OR] 1.23, 95% confidence interval [CI] 1.06-1.42). Genotype distributions were also different between cases and controls (C/T+T/T [abnormal]: 174 of 278 [63%]; C/C [normal]: 104 of 278 [37%] compared with C/T+T/T: 728 of 1,397 [52%]; C/C 669 of 1,397 [48%]; P=.002; OR 1.54, 95% CI 1.18-2.02). The clinical effect of the MTHFR C677T polymorphism was restricted to women with SGA infants (P=.05; OR 1.33, 95% CI 1.00-1.77). No significant differences in genotype distributions were observed among women with intrauterine fetal death, preeclampsia, and preterm delivery.

CONCLUSION

MTHFR C677T is a genetic marker for identifying women at increased risk of SGA infants.

LEVEL OF EVIDENCE

II.

Folic acid: influence on the outcome of pregnancy

The periconceptional use of folic acid-containing supplements reduces the first occurrence, as well as the recurrence, of neural tube defects. Women of populations in which adverse pregnancy outcomes are prevalent often consume diets that contain a low density of vitamins and minerals, including folate. Folate intake may need to be sustained after complete closure of the neural tube to decrease the risk of other poor pregnancy outcomes. A central feature of embryonic and fetal development is widespread cell division; folate is central because of its role in nucleic acid synthesis. During gestation, marginal folate nutriture can impair cellular growth and replication in the fetus or placenta. Folate deficiency can occur because dietary folate intake is low or because the metabolic requirement for folate is increased by a particular genetic defect or defects. During pregnancy, low concentrations of dietary and circulating folate are associated with increased risks of preterm delivery, infant low birth weight, and fetal growth retardation. A metabolic effect of folate deficiency is an elevation of blood homocysteine. Likewise, the presence of maternal homocysteine concentrations have been associated both with increased habitual spontaneous abortion and pregnancy complications (eg, placental abruption and preeclampsia), which increase the risk of poor pregnancy outcome and of decreased birth weight and gestation duration.

Growth, development and differentiation: a functional food science approach

Few other aspects of food supply and metabolism are of greater biological importance than the feeding of mothers during pregnancy and lactation, and of their infants and young children. Nutritional factors during early development not only have short-term effects on growth, body composition and body functions but also exert long-term effects on health, disease and mortality risks in adulthood, as well as development of neural functions and behaviour, a phenomenon called 'metabolic programming'. The interaction of nutrients and gene expression may form the basis of many of these programming effects and needs to be investigated in more detail. The relation between availability of food ingredients and cell and tissue differentiation and its possible uses for promoting health and development requires further exploration. The course of pregnancy, childbirth and lactation as well as human milk composition and the short- and long-term outcome of the child are influenced by the intake of foods and particularly micronutrients, e.g. polyunsaturated fatty acids, Fe, Zn and I. Folic acid supplementation from before conception through the first weeks of pregnancy can markedly reduce the occurrence of severe embryonic malformations; other potential benefits of modulating nutrient supply on maternal and child health should be further evaluated. The evaluation of dietary effects on child growth requires epidemiological and field studies as well as evaluation of specific cell and tissue growth. Novel substrates, growth factors and conditionally essential nutrients (e.g. growth factors, amino acids, polyunsaturated fatty acids) may be potentially useful as ingredients in functional foods and need to be assessed carefully. Intestinal growth, maturation, and adaptation as well as long-term function may be influenced by food ingredients such as oligosaccharides, gangliosides, high-molecular-mass glycoproteins, bile salt-activated lipase, pre- and probiotics. There are indications for some beneficial effects of functional foods on the developing immune response, for example induced by antioxidant vitamins, trace elements, fatty acids, arginine, nucleotides, and altered antigen contents in infant foods. Peak bone mass at the end of adolescence can be increased by dietary means, which is expected to be of long-term importance for the prevention of osteoporosis at older ages. Future studies should be directed to the combined effects of Ca and other constituents of growing bone, such as P, Mg and Zn, as well as vitamins D and K, and the trace elements F and B. Pregnancy and the first postnatal months are critical time periods for the growth and development of the human nervous system, processes for which adequate substrate supplies are essential. Early diet seems to have long-term effects on sensory and cognitive abilities as well as behaviour. The potential beneficial effects of a balanced supply of nutrients such as I, Fe, Zn and polyunsaturated fatty acids should be further evaluated. Possible long-term effects of early exposure to tastes and flavours on later food choice preferences may have a major impact on public health and need to be further elucidated. The use of biotechnology and recombinant techniques may offer the opportunity to include various bioactive substances in special dietary products, such as human milk proteins, peptides, growth factors, which may have beneficial physiological effects, particularly in infancy and early childhood.

Folate economy in pregnancy

Pregnant women are prone to becoming folate deficient because there is a significant increase in folate requirement during pregnancy and folate intakes of pregnant women are often insufficient. Reduced folate levels in blood and neutrophilic hypersegmentation reflect a negative folate balance. Possible consequences of a low maternal folate status may be pregnancy complications such as abortion, abortus imminens, abruptio placentae, and congenital malformations. The role of folic acid in the etiology of neural tube defects has been discussed for decades. The importance of an adequate maternal folate status in the prevention of neural tube defects has been demonstrated by observational and controlled intervention trials. However, the mechanism of the protective effect of periconceptional folate supplementation is not completely understood. Metabolic disorders are probably involved in the pathogenesis of neural tube defects so that a relative folate shortage rather than folate deficiency seems to be responsible for the disturbed neural tube development, which can be compensated for by a higher folate intake.