Vitamin levels in pregnancy are generally managed through dietary and supplement intake but are also influenced by genetic polymorphisms (two or more gene variants in a specific DNA sequence), which can modify enzyme activity involved in vitamin metabolism and transport, according to the authors of a recent study.
Some gene polymorphisms initiate disturbances in B9 and B12 vitamin status, however testing pregnant women for disruptive gene variants could enable personalised treatments to prevent deficiencies and foetal abnormalities, they say.
“Determining genetic variants in folate and cobalamin metabolism-related genes in pregnant women can lead to personalised treatment with higher amounts of folic acid and cobalamin for the sake of improving pregnancy and neonatal health outcomes.”
Different gene variants have been linked to vitamin deficiencies but their prevalence in the general population is unknown.
Spanish researchers set out to analyse the genotype of 149 pregnant women with similar pre- to post-natal backgrounds in relation to conception, pregnancy, delivery, and new-born complications, to assess the prevalence of four genetic polymorphisms of B9 and B12 metabolism (methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR), cubilin (CUBN), and SLC19A1 – also known as reduced folate carrier or RFC1).
All women received folic acid supplementation in the first trimester of pregnancy: 81.2% received a multivitamin complex that included folic acid, iodine, and B12, while 13.4% received folic acid plus iodine, and 5.4% just folic acid. In addition, 55% of women were prescribed iron supplementation.
Notable findings revealed a higher frequency of ‘assisted fertilisation’, pre-eclampsia and pre-term birth in women carrying the MTHFR gene variant and a significantly lower incidence of delivery complications among CUBN carriers.
In total, 61% of participants carried risk alleles (gene variants) in the MTHFR gene, 72% in the SCL19A1 gene, and 47% in the CUBN gene. The majority also carried the reference allele for the MTR (99%), although only 1% were risk genotype carriers of this gene.
The prevalence of MTHFR thymine-thymine (TT) polymorphism was found in 57% of participants. This variant has known risk factors for a number of conditions, including hypertension, blood clots and certain types of cancer.
Dysfunction of the MTHFR enzyme also produces elevated homocysteine, increasing the risk of spontaneous abortion.
The authors commented: “Women with the MTHFR TT genotype are predisposed to elevated homocysteine levels when folic acid intake is inadequate, endothelial damage, arterial constriction, and thrombosis, all of which can lead to placental hypoperfusion resulting in worse neonatal outcomes with pre-term birth (PTB) and low birth weight (LBW).”
Limitations and outcomes
Study limitations include the small sample size and short follow-up. There was also a high incidence of gestational diabetes mellitus (GDM) among participants, compared to the general population, and there was no metabolic data to assess the consequences of metabolism of single carbons, which limits the significance of the analyses.
However, given the results, the authors postulate that the prevalence of specific genetic variants is related to mother and neonatal outcomes.
“Our data show a high prevalence of genetic variants related to folic acid and vitamin B12 metabolic genes in pregnant women that may justify the difference in maternal and neonatal outcomes,” they write.
“Knowing the prevalence of these polymorphisms may lead to a personalised prescription of vitamin intake.”
Published online: https://doi.org/10.3390/nu14132702
‘Genetic Variants in Folate and Cobalamin Metabolism-Related Genes in Pregnant Women of a Homogeneous Spanish Population: The Need for Revisiting the Current Vitamin Supplementation Strategies’
Gemma Rodriguez-Carnero et al.