Folinic Acid Supplementation During Pregnancy in Two Women with Folate Receptor Alpha Autoantibodies: Potential Prevention of Autism Spectrum Disorder in Offspring

Abstract

This report presents two cases of pregnant women positive for folate receptor alpha (FRα) autoantibodies who received folinic acid supplementation. Both had previously given birth to children diagnosed with autism spectrum disorder (ASD). In subsequent pregnancies, folinic acid was administered preconceptionally and continually throughout gestation. The resulting offspring, monitored up to three years of age, exhibited typical neurodevelopment with no signs of ASD. These cases suggest that folinic acid supplementation during pregnancy may mitigate the risk of ASD in children born to mothers with FRα autoantibodies.

1. Introduction

The prevalence of autism spectrum disorder (ASD) has risen markedly, with recent estimates indicating that approximately 1 in 36 children are affected [1].

Growing evidence implicates not only genetic but also immune-mediated mechanisms in the pathogenesis of ASD, particularly during fetal development [2,3,4]. In particular, autoantibodies against the folate receptor alpha (FRAA) have been shown to interfere with folate transport across the placental and blood–brain barriers, impairing folate delivery to the fetal central nervous system and increasing the risk of ASD and cognitive impairments in offspring [4,5,6]. The presence of blocking and/or binding autoantibodies against the folate receptor alpha (FRα) in the serum constitutes a key pathogenic mechanism in cerebral folate deficiency syndromes (CFDS) [7]. Blocking autoantibodies prevent folate from binding the receptor, while binding autoantibodies may induce receptor internalization or activate complement-mediated inflammation, further impairing folate transport. These disruptions result in reduced levels of 5-methyltetrahydrofolate (5-MTHF) in the cerebrospinal fluid despite normal systemic folate levels, leading to neurological and neuropsychiatric symptoms, including ASD, infantile-onset cerebral folate deficiency, spastic ataxic syndromes, dystonia, Rett syndrome, and other neurodevelopmental and psychiatric disorders. Folate (vitamin B9) is essential for DNA synthesis, epigenetic methylation, and neurogenesis during fetal and postnatal brain development. The active form, 5-MTHF, crosses the blood–brain barrier primarily via FRα, which is highly expressed in the choroid plexus. FRAA-mediated blockade of FRα thus causes cerebral folate deficiency (CFD), characterized by impaired folate delivery to the brain [8]. While prenatal folic acid supplementation has significantly reduced neural tube defects, it is often insufficient in FRAA-positive pregnancies, where receptor blockade limits folate transport. Folinic acid, an active form of folate, can bypass this blockade by utilizing alternative transporters such as the reduced folate carrier (RFC), thus providing adequate folate support to the fetal nervous system. Preclinical and clinical studies suggest that folinic acid supplementation in FRAA-positive pregnant women can significantly improve neuropsychiatric outcomes in their children, reducing the incidence of ASD and learning disabilities [5,9,10].

Therefore, the early diagnosis of FRAA and implementation of targeted folinic acid treatment represent promising strategies for preventing adverse neurological outcomes in at-risk populations, emphasizing the importance of randomized clinical trials to define optimal protocols.

This report aims to contribute to the growing body of evidence on the role of folate receptor alpha autoantibodies in neurodevelopmental disorders. By presenting two clinical cases of FRAA-positive mothers treated with folinic acid during pregnancy, we explore the potential preventive impact on autism spectrum disorder (ASD) in offspring. Our goal is to highlight the need for further research and support the rationale for early detection and targeted intervention in high-risk pregnancies.

2. Case Presentations

A 32-year-old woman with two children—one with significant language delay and dyslexia, and another with severe ASD—sought preconception counseling in June 2021. Testing revealed the presence of folate receptor alpha (FRα) autoantibodies at levels of 90 ng/mL at three months and 130 ng/mL at eight months. She commenced oral calcium folinate at a dose of 7.5 mg/day two months prior to conception and continued taking it throughout pregnancy. At 38 weeks gestation, she delivered a male infant via cesarean section, weighing 3150 g, with Apgar scores of 10 at both 1 and 5 min. Developmental assessments, including the Autism Diagnostic Observation Schedule (ADOS) at age three, indicated typical development with no signs of ASD. Similarly, a 28-year-old woman, S.R., whose previous child had been diagnosed with pervasive developmental disorder-not otherwise specified (PDD-NOS), presented at five weeks gestation in October 2021. FRα autoantibody testing was positive at levels of 170 ng/mL at three months and 165 ng/mL at eight months. She began calcium folinate supplementation at 7.5 mg/day and continued taking it throughout pregnancy. She delivered a male infant at term via spontaneous vaginal delivery, weighing 3800 g. At age three, the child was evaluated with the ADOS and showed no features consistent with ASD. Written informed consent was obtained from both patients for publication of this case report and any accompanying images. Human anti-FOLR (folate receptor autoantibodies, IgG) levels were measured in serum using a commercially available ELISA kit, with a sensitivity of 3.3 ng/mL and a detection range of 7.82–500 ng/mL. FRα autoantibodies were quantified with the Human anti-FOLR ELISA (ELK-Biotechnology; RUO between 2021 and 2022, CE-IVD since 2025). Control participants underwent testing with this method to establish a cutoff value of 30 ng/mL (The cut-off value was derived from the analysis of 412 women with no history of ASD), above which samples were classified as positive. This threshold clearly distinguished individuals with elevated anti-FOLR antibody levels and was subsequently used to assess positivity within the study population. Additionally, genetic analyses, including whole-exome sequencing (WES) of approximately 19,000 genes and a comparative genomic hybridization (CGH) array—were performed on both mothers and their offspring. All genetic tests yielded negative results, reinforcing the uniqueness of this case and effectively excluding known penetrant genetic etiologies.

3. Discussion

These cases underscore the potential role of maternal folate receptor alpha (FRα) autoantibodies in the etiology of autism spectrum disorder (ASD) and suggest that folinic acid supplementation during pregnancy may confer neuroprotective effects. FRα autoantibodies have been associated with impaired folate transport across the blood–brain barrier, leading to cerebral folate deficiency (CFD)—a condition documented in individuals with ASD [11]. Folinic acid, a reduced and active form of folate, can circumvent the FRα-mediated transport system by utilizing alternative cellular uptake mechanisms. Specifically, folinic acid enters the central nervous system through the reduced folate carrier (RFC) and the proton-coupled folate transporter (PCFT), which are not blocked by FRα autoantibodies. These transporters ensure adequate folate availability in the cerebrospinal fluid, thereby facilitating essential neurodevelopmental processes such as dendritic growth, synaptogenesis, and myelination [12,13]. While previous studies have demonstrated the therapeutic benefits of folinic acid in improving communication and cognitive outcomes in children with ASD [14], this report presents, to our knowledge, the first longitudinal observation suggesting a preventive effect of folinic acid when administered during pregnancy to mothers with FRα autoantibodies. This aligns with broader epidemiological data showing that periconceptional folic acid supplementation significantly reduces the risk of ASD in offspring [15,16,17].

These findings open up a promising avenue for targeted prevention in at-risk populations and underscore the importance of identifying FRα autoantibodies in women with a history of ASD in offspring or other neurodevelopmental disorders. Despite the valuable clinical insights provided by these cases, our study has important limitations beyond sample size and follow-up. In particular, no cerebrospinal fluid, cord blood, or amniotic fluid samples were collected during pregnancy, precluding direct assessment of fetal folate levels or placental transfer of folinic acid. Furthermore, due to the retrospective nature of the study and the unavailability of stored samples, we were unable to perform post hoc testing for additional folate-related or autoimmune biomarkers. These omissions limit our ability to fully assess the biological plausibility and mechanisms underlying our observations. In addition, we do not have antibody measurements from the preconception period; the available data refers only to the third and eighth months of gestation. We recognize the importance of distinguishing antibody levels before and during pregnancy, as this may provide further insights into maternal immune status and treatment timing. This aspect represents another area for improvement in future prospective studies. The follow-up period, while extending to three years, may not capture all potential neurodevelopmental outcomes that could manifest later in childhood. Larger, controlled studies are necessary to validate these preliminary observations, to better understand the pathophysiology of FRα autoantibodies in pregnancy, and to establish definitive guidelines for folinic acid supplementation as a preventive therapy.

4. Conclusions

This report highlights the potential preventive role of folinic acid supplementation during pregnancy in women positive for folate receptor alpha (FRα) autoantibodies. The two cases presented suggest that early and continuous folinic acid administration may mitigate the risk of autism spectrum disorder (ASD) in offspring, likely by bypassing the impaired folate transport caused by these autoantibodies. This intervention could represent a promising targeted strategy for neuroprotection in at-risk pregnancies, emphasizing the need for screening for FRα autoantibodies in women with a history of ASD or related neurodevelopmental disorders.