Neural Tube Defects and Associated Anomalies before and after Folic Acid Fortification

Is the Tradeoff between Folic Acid or/and Multivitamin Supplementation against Birth Defects in Early Pregnancy Reconsidered? Evidence Based on a Chinese Birth Cohort Study

BACKGROUND

Several studies have reported conflicting results on the association between maternal exposure to folic acid (FA) and/or multivitamin (MV) supplements and the risk of birth defects (BDs), especially for different subtypes of BDs. The present study aimed to identify the association between maternal exposure to FA or/and MV and BDs in offspring.

METHODS

In the Chinese Birth Cohort Study initiated from 20 November 2017, 120,652 pregnant women completed follow-up until 20 August 2021. The participants were classified into four groups: without exposure to FA and MV, exposure to only FA, exposure to only MV, and exposure to FA and MV. Birth defects were coded by the International Classification of Diseases (ICD)-10. In order to explore the structural relationship between maternal FA or MV supplements and BDs, directed acyclic graphs were drawn. Then, an inverse probability treatment weighting was utilized to reduce the systematic differences in the baseline characteristics among the different groups. Lastly, a two-level mixed-effect log binomial regression analysis was used to estimate the relative risk (RR) value of the different subtypes of BDs under different exposures to FA and/or MV.

RESULTS

Compared with the maternal group without exposure to FA and MV, the RR values of nervous system defects, face, ear, and neck defects, limb defects, and CHDs in the maternal group with only FA supplementation were less than 1.0, but they were not statistically significant. The RR values of genitourinary defects, abnormal chromosomes, and oral clefts were more than 1.0, and they were also not statistically significant. However, the risk of genitourinary defects (RR: 3.22, 95% CI: 1.42-7.29) and chromosomal abnormalities (RR: 2.57, 95% CI: 1.16-5.73) in the maternal group with only MV supplementation increased more than those in the maternal group without exposure to FA and MV. In addition, the RR values of all subtypes of BDs in the maternal group with exposure to FA and MV were closer to 1.0 than those in maternal group with exposure to only MV, but they were not statistically significant.

CONCLUSIONS

It was indicated that the simultaneous supplementation of FA and MV in early pregnancy may have an interaction for the prevention of BDs and may have inconsistent effects for different subtypes of BDs. At the same time, excessive FA supplementation in pregnant women may increase the risk of BDs in their offspring. Although the mechanism is not clear, this evidence reminded us that more trade-offs are necessary for formulating strategies for the prevention of BDs with FA and/or MV supplementation in early pregnancy.

NAD+ deficiency in human congenital malformations and miscarriage: A new model of pleiotropy

Pleiotropy is defined as the phenomenon of a single gene locus influencing two or more distinct phenotypic traits. However, nicotinamide adenine dinucleotide (NAD+) deficiency through diet alone can cause multiple or single malformations in mice. Additionally, humans with decreased NAD+ production due to changes in pathway genes display similar malformations. Here, I hypothesize NAD+ deficiency as a pleiotropic mechanism for multiple malformation conditions, including limb-body wall complex (LBWC), pentalogy of Cantrell (POC), omphalocele-exstrophy-imperforate anus-spinal defects (OEIS) complex, vertebral-anal-cardiac-tracheoesophageal fistula-renal-limb (VACTERL) association (hereafter VACTERL), oculoauriculovertebral spectrum (OAVS), Mullerian duct aplasia-renal anomalies-cervicothoracic somite dysplasia (MURCS), sirenomelia, and urorectal septum malformation (URSM) sequence, along with miscarriages and other forms of congenital malformation. The term Congenital NAD Deficiency Disorder (CNDD) could be considered for patients with these malformations; however, it is important to emphasize there have been no confirmatory experimental studies in humans to prove this hypothesis. In addition, these multiple malformation conditions should not be considered individual entities for the following reasons: First, there is no uniform consensus of clinical diagnostic criteria and all of them fail to capture cases with partial expression of the phenotype. Second, reports of individuals consistently show overlapping features with other reported conditions in this group. Finally, what is currently defined as VACTERL is what I would refer to as a default label when more striking features such as body wall defects, caudal dysgenesis, or cloacal exstrophy are not present.

A SOX3 duplication and lumbosacral spina bifida in three generations

Chromosomal aneuploidies, microduplications and microdeletions are the most common confirmed genetic causes of spina bifida. Microduplications of Xq27 containing the SOX3 gene have been reported in 11 cases, confirming the existence of an X-chromosomal locus for spina bifida. A three generation kindred reported here with a SOX3 duplication has been identified in one of 17 kindreds with recurrences in the 29 years of the South Carolina Neural Tube Defect Prevention Program. Other recurrences during this time period included siblings with an APAF1 mutation, siblings with a CASP9 mutation, siblings with a microdeletion of 13q, and two sets of siblings with Meckel syndrome who did not have genetic/genomic studies performed.

Mapping of folic acid in the children brainstem

Using highly specific antisera, the neuroanatomical distribution of folic acid (FA) and retinoic acid (RA) has been studied for the first time in the children brainstem. Neither immunoreactive structures containing RA nor immunoreactive fibers containing FA were found. FA-immunoreactive perikarya (fusiform, small/medium in size, one short dendrite) were only found in the pons in three regions: central gray, reticular formation, and locus coeruleus. The number of cell bodies decreased with age. In the first case studied (2 years), a moderate density of cell bodies was observed in the central gray and reticular formation, whereas a low density was found in the locus coeruleus. In the second case (6 years), a low density of these perikarya was observed in the central gray, reticular formation, and locus coeruleus. In the third case (7 years), a low density of FA-immunoreactive cell bodies was found in the central gray and reticular formation, whereas in the locus coeruleus no immunoreactive cell bodies were observed. The distribution of FA in the central nervous system of humans and monkeys is different and, in addition, in these species the vitamin was located in different parts of the nerve cells. The restricted distribution of FA suggests that the vitamin is involved in specific physiological mechanisms.