Folic Acid Intake, Fetal Brain Growth, and Maternal Smoking in Pregnancy: A Randomized Controlled Trial

Maternal Smoking during Pregnancy and its effects on Neural Tube Defects

Objectives

Maternal smoking is a potent teratogen among congenital malformations, however its role in the development of Neural Tube Defects (NTDs) is still unclear. In this systematic review, we intend to further investigate the interaction of smoking during pregnancy and the incidence of NTDs.

Materials & Methods

This article was written according to PRISMA criteria from February 2015 and August 2022. After examining the four stages of PRISMA criteria, we selected clinical articles. These articles were selected from PubMed, Scopus and Google scholar (for results follow-up) databases. We gathered NTDs effect and types, smoking type and habit of parents, from neonates.

Results

Eventually, 8 articles were included by two separated authors, Smoking was associated with an increase NTDs in the population of pregnant mothers and also among children whose fathers smoked. The main side effects that were considered to be the cause of NTDs besides smoking were alcohol and BMI (18.5-24.9). Smoking also affects the level of folic acid as a substance with an essential role that affects the closure of the neural tube. folic acid available to infants changing along with the level of other blood elements such as zinc, that necessary prevent for NTDs condition.

Conclusion

Parental smoking can be considered as one of the strong teratogens in the occurrence of NTDs. Smoking, whether active or passive by the mother, or by the father, is associated with the occurrence of NTDs, In order to reduce the prevalence this disorder, we advise pregnant mothers and neonate's fathers to quit smoking.

Risk of Excess Maternal Folic Acid Supplementation in Offspring

Folate, also known as vitamin B9, facilitates the transfer of methyl groups among molecules, which is crucial for amino acid metabolism and nucleotide synthesis. Adequate maternal folate supplementation has been widely acknowledged for its pivotal role in promoting cell proliferation and preventing neural tube defects. However, in the post-fortification era, there has been a rising concern regarding an excess maternal intake of folic acid (FA), the synthetic form of folate. In this review, we focused on recent advancements in understanding the influence of excess maternal FA intake on offspring. For human studies, we summarized findings from clinical trials investigating the effects of periconceptional FA intake on neurodevelopment and molecular-level changes in offspring. For studies using mouse models, we compiled the impact of high maternal FA supplementation on gene expression and behavioral changes in offspring. In summary, excessive maternal folate intake could potentially have adverse effects on offspring. Overall, we highlighted concerns regarding elevated maternal folate status in the population, providing a comprehensive perspective on the potential adverse effects of excessive maternal FA supplementation on offspring.

A Female Newborn With Occipital Encephalocele and a Hypoplastic Right Ventricle Secondary to Tricuspid and Pulmonary Atresia: A Case Report

Encephaloceles and severe cardiac malformations are rare presentations in a newborn. The mechanism of these congenital abnormalities is relatively unknown, but it is hypothesized to be related to genetic, environmental, and maternal risk factors. This case report describes a newborn with an occipital encephalocele associated with severe right ventricular hypoplasia secondary to tricuspid and pulmonary atresia. The patient's maternal risk factors included obesity, type 2 diabetes mellitus, and everyday tobacco use during pregnancy. Education on preconception planning, management, and counseling is essential as a preventative measure in fetal development and is further emphasized in this case.

OUP accepted manuscript

STUDY QUESTION

Is periconceptional maternal smoking associated with embryonic morphological development in ongoing pregnancies?

SUMMARY ANSWER

Smoking during the periconceptional period is associated with a delayed embryonic morphological development which is not fully recuperated beyond the first trimester of pregnancy.

WHAT IS KNOWN ALREADY

Smoking during pregnancy decreases prenatal growth, increasing the risk of preterm birth, small for gestational age (GA) and childhood obesity.

STUDY DESIGN, SIZE, DURATION

Between 2010 and 2018, 689 women with ongoing singleton pregnancies were periconceptionally enrolled in a prospective cohort study with follow-up until 1 year after delivery.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Between 7 + 0 and 10 + 3 weeks, GA serial three-dimensional transvaginal ultrasound scans were performed. Embryonic morphological development as assessed by the Carnegie developmental stages was evaluated using Virtual Reality techniques. In the absence of fetal morphology classification methods beyond the embryonic period, fetal ultrasound measurements at around 20 weeks’ GA, and birth weight were used to assess fetal growth. Linear mixed models were used to evaluate the association between smoking and the Carnegie stages. Regarding first-trimester morphological development, we additionally stratified our findings for mode of conception. Multiple linear regression models were used to study the association between smoking, fetal growth and birth weight. To investigate to which extent delayed embryonic morphological development mediated the effect of smoking, contemporary mediation analysis was used. Adjustments were made for potential confounders and other covariates.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 689 singleton ongoing pregnancies were included and 1210 Carnegie stages were determined. Maternal periconceptional smoking represented by the number of cigarettes/day was associated with a slight non-significant delay of the Carnegie stages (β_{cigarettes/day} = −0.058, 95% CI −0.122; 0.007, P = 0.080). Smoking of ≥10 cigarettes/day showed the strongest association (β_{≥10 cigarettes/day} = −0.352, 95% CI −0.648; −0.057, P = 0.019), as reflected by a 0.9-day delay in reaching the final Carnegie stage. Stratification for mode of conception showed a stronger negative association between the number of cigarettes/day in the IVF/ICSI group (β_{cigarettes/day} = −0.126, 95% CI −0.200; −0.051, P = 0.001) compared to naturally conceived pregnancies (β_{cigarettes/day} = 0.009, 95% CI −0.093; 0.111, P = 0.867). In the IVF/ICSI group, periconceptional smoking of ≥10 cigarettes/day was associated with in a 1.6 day delay in reaching the final Carnegie stage (β_{≥10 cigarettes/day} = −0.510, 95% CI −0.834; −0.186, P = 0.002). In the second trimester, periconceptional smoking was associated with a smaller femur length (β_{cigarettes/day} = −0.077, 95% CI −0.147; −0.008, P = 0.029) and a larger head circumference (β_{1–9 cigarettes/day} = 0.290, 95% CI 0.065; 0.514, P = 0.012). Smoking was associated with a lower birth weight, with a dose-response effect (β_{cigarettes/day} = −0.150, 95% CI −0.233; −0.068, P < 0.001). Furthermore, using the unadjusted model, 40–60% of the association between smoking and fetal ultrasound parameters and 6.3% of the association between smoking and birth weight can be explained by a delayed embryonic morphology.

LIMITATIONS, REASONS FOR CAUTION

The study population was recruited from a tertiary referral center. Smoking habits were explored using self-reported questionnaires and checked for consistency by trained researchers.

WIDER IMPLICATIONS OF THE FINDINGS

This study shows that the association of periconceptional maternal smoking and human morphological development can already be detected early in the first trimester of pregnancy using embryonic morphology as outcome. One of the key messages of this study is that the delay, or dysregulation, in embryonic morphology is associated with allometric growth reflected by smaller fetal measurements at 20 weeks gestation and lower weight at birth. The delay in embryonic morphology, measured in early pregnancy, cannot be recuperated during the pregnancy. The results of this study emphasize the importance of smoking intervention programs prior to conception. More research is warranted to assess the association between periconceptional smoking cessation and embryonic development.

STUDY FUNDING/COMPETING INTEREST(S)

The work was funded by the Department of Obstetrics and Gynaecology, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands. The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Maternal One-Carbon Metabolism during the Periconceptional Period and Human Foetal Brain Growth: A Systematic Review

The maternal environment during the periconceptional period influences foetal growth and development, in part, via epigenetic mechanisms moderated by one-carbon metabolic pathways. During embryonic development, one-carbon metabolism is involved in brain development and neural programming. Derangements in one-carbon metabolism increase (i) the short-term risk of embryonic neural tube-related defects and (ii) long-term childhood behaviour, cognition, and autism spectrum disorders. Here we investigate the association between maternal one-carbon metabolism and foetal and neonatal brain growth and development. Database searching resulted in 26 articles eligible for inclusion. Maternal vitamin B6, vitamin B12, homocysteine, and choline were not associated with foetal and/or neonatal head growth. First-trimester maternal plasma folate within the normal range (>17 nmol/L) associated with increased foetal head size and head growth, and high erythrocyte folate (1538-1813 nmol/L) with increased cerebellar growth, whereas folate deficiency (<7 nmol/L) associated with a reduced foetal brain volume. Preconceptional folic acid supplement use and specific dietary patterns (associated with increased B vitamins and low homocysteine) increased foetal head size. Although early pregnancy maternal folate appears to be the most independent predictor of foetal brain growth, there is insufficient data to confirm the link between maternal folate and offspring risks for neurodevelopmental diseases.