Immunobiology of pregnancy: from basic science to translational medicine

Antiphospholipid antibodies inhibit the migration and invasion of trophoblast cells by suppressing the JNK/C-Jun/MMP1 signaling pathway

BACKGROUND

Antiphospholipid syndrome (APS) is an autoimmune disease primarily manifested by recurrent thrombosis and pregnancy-related complications. The migration and invasion abilities of trophoblast cells play a crucial role in maintaining normal pregnancy. It is now increasingly recognized that adverse pregnancy outcomes in APS are associated with the disruption of trophoblast function by aPL (antiphospholipid antibodies), rather than thrombotic occlusion of the placental vasculature. Therefore, this article aimed to explore the potential mechanisms by which aPL affect trophoblast cell function.

METHOD

An APS cell model was established in the HTR-8 trophoblast cell line, followed by RNA sequencing to identify key genes involved in trophoblast cell function. To explore the underlying mechanisms, we employed quantitative real-time PCR, Western blotting, immunohistochemistry, ELISA, plasmid transfection and KEGG pathway enrichment analysis. Functional assays, including migration and invasion tests, were conducted to evaluate trophoblast cell ability. Clinical samples were collected, and the expression levels of target molecules in serum were quantified using ELISA. Additionally, an APS animal pregnancy model was developed to assess pregnancy loss rates and analyze the expression of specific target genes in the placenta.

RESULTS

Sequencing analysis revealed significant downregulation of MMP1 in the APS model, confirmed by qPCR and Western blotting. Correspondingly, migration and invasion of HTR-8 cells were impaired in the APS group, but MMP1 overexpression restored trophoblast cell function. Serum MMP1 levels were lower in APS patients than in controls. In the animal pregnancy model, the APS group exhibited higher pregnancy loss, with placental immunohistochemistry confirming decreased MMP1 expression. KEGG enrichment analysis of differentially expressed genes between the NC and APS groups revealed a significant difference in the MAPK pathway, with P-JNK showing the most notable reduction. C-Jun, a downstream regulator of JNK, also decreased and modulated MMP1 expression. Notably, Anisomycin treatment increased P-C-Jun, upregulated MMP1, and enhanced trophoblast migration and invasion.

CONCLUSION

APL downregulated MMP1 expression by suppressing the JNK/C-Jun signaling pathway in trophoblast cells, thereby reducing their migratory and invasive capabilities. This represent a potential pathogenic mechanism contributing to adverse pregnancy outcomes in APS patients, highlighting possible therapeutic targets for intervention in APS management.

A novel long-acting phospholipid phase transition gel with progesterone effectively promoted uterine development

Progesterone (PRG), a steroidal hormone, is commonly utilized in the clinical practice of obstetrics and gynecology. The high frequency of PRG injections, however, has brought significant pain and inconvenience to patients. In this study, we developed a long-acting injection leveraging the phase transition mechanism for the long-term treatment in Assisted Reproductive Technology (ART). The components we selected all possess excellent biocompatibility. Pharmacokinetic studies revealed that the PRG-loaded phospholipid phase transition gels (PRG-PPTGs) released the PRG continuously for over 7 days. Notably, pharmacological investigation demonstrated that PRG-PPTGs, when administered weekly, effectively promoted uterine development. Our findings suggested that PRG-PPTGs successfully achieve both the prevention of burst release and the reduction of dosing frequency, highlighting the potential of PPTGs as promising long-acting composite system for hydrophobic drugs.

[Use of hydroxychloroquine in recurrent immune-mediated obstetric diseases (excluding systemic lupus): Scientific basis and evidence]

Hydroxychloroquine (HCQ), a synthetic antimalarial, is recognized for its immunomodulatory, anti-inflammatory and vascular-protective effects. In 20-30% of cases of primary obstetrical antiphospholipid syndrome (APS), the combination of antiplatelet aggregation and prophylactic anticoagulation fails to prevent obstetrical complications, a situation referred to as refractory obstetrical APS. This is partly due to the pro-inflammatory effects of antiphospholipid antibodies (aPL) binding to decidual and trophoblastic cells, which compromise embryonic implantation and placentation. Experimental studies in vitro and in mouse models have shown that HCQ can inhibit the detrimental effect of aPLs on trophoblastic invasion, findings corroborated by retrospective observational clinical studies. However, no randomized controlled trial has evaluated the addition of HCQ to conventional therapy for refractory obstetric APS. The hypothesis of allo-immune and/or autoimmune mechanisms involved in cases of recurrent pregnancy loss (RPL) with no identified cause and in chronic intervillositis of unknown etiology (CIUE) has led to the empirical use of HCQ in these indications. However, current evidence does not support its use in unexplained RPL. A few clinical studies of low scientific evidence suggest a benefit of HCQ in CIUE, but further data are needed. Finally, pre-eclampsia (PE) is another pregnancy-related condition at risk of recurrence, and its pathogenesis also seems to involve an imbalance in immune responses. HCQ's antioxidant properties could have a positive effect on endothelial dysfunction, a key component of PE.

Association between monocyte-to-lymphocyte ratio and cardiovascular diseases: insights from NHANES data

BACKGROUND

This study intends to examine any possible correlation between monocyte-to-lymphocyte ratio (MLR) and cardiovascular diseases (CVD).

METHODS

Data from the 1999-2020 National Health and Nutrition Examination Survey (NHANES) in the USA were analyzed. Heart attacks, angina pectoris, congestive heart failure (CHF), coronary heart disease (CHD), and stroke were all covered by CVD. The independent relationships between these cardiovascular events and MLR levels, as well as other inflammatory indices (system inflammation response index (SIRI), aggregate index of systemic inflammation (AISI), and C-reactive protein-to-albumin ratio (CAR)), were investigated. Furthermore, interaction tests and subgroup analysis were performed. Diagnostic capacities were also predicted and compared using receiver operating characteristic (ROC) curves.

RESULTS

Males made up 49.63% of the 46,289 people who were recruited in this study. The prevalence of CVD and its events were as follows: CHF at 2.99%, CHD at 3.72%, angina pectoris at 2.57%, heart attacks at 3.94%, and stroke at 3.48%, with CVD itself at 7.98%. MLR and CVD were positively correlated. Specifically, smooth curve fittings also found a non-linear relationship between MLR and CVD. Moreover, higher MLR levels were linked to increased rates of CHF, CHD, and strokes. SIRI was also found to have a positive correlation with CVD. MLR outperformed other inflammatory indices (SIRI, AISI, and CAR) in terms of discriminative capacity and accuracy in predicting CVD, CHF, CHD, angina pectoris, heart attack, and stroke, according to ROC analysis.

CONCLUSIONS

Compared with other inflammatory indicators (SIRI, AISI, and CAR), MLR appears to be a better inflammatory index for predicting CVD, CHF, CHD, angina pectoris, heart attack, and stroke. American adults with elevated MLR and SIRI should be aware of the possible harm caused by CVD. Causal inference is, however, limited by the cross-sectional design and dependence on self-reported data. Further longitudinal studies are needed to validate these findings.

MicroRNA-155 targets p65 to regulate PD-L1 expression in the early pregnancy endometrium

Reproductive disorders in dairy cows represent a significant challenge to the advancement of the dairy industry. Pregnancy success is closely related to the mechanism of immune tolerance, with the PD-1/PD-L1 signaling pathway playing a role in immune regulation, which is associated with immune tolerance and pregnancy maintenance. MicroRNAs can regulate pivotal molecules within the signaling pathway, physiological activities, and disease processes. p65 and PD-L1 expression was significantly increased in the early pregnant uterine epithelium. In contrast, the expression of p65 and PD-L1 was homogeneous in the endometrial epithelium of E2 and P4 co-stimulated bEECs and changed with the stimulation time and concentration. MiR-155 expression was significantly reduced in the early pregnant uterine epithelium. p65 was identified as a molecular target of miR-155 using a dual luciferase assay and mimics/inhibitor transfection, and miR-155 inhibited p65 expression by binding to the 3'-UTR of p65 mRNA. The regulation of PD-L1 expression by p65 was confirmed through the knockdown of p65 by si-p65 and the overexpression of p65 by pcDNA3.1-p65. In the context of pregnancy, miR-155 was observed to target p65, thereby regulating PD-L1 expression at the endometrial epithelium.

Exploring the Immunological Aspects and Treatments of Recurrent Pregnancy Loss and Recurrent Implantation Failure

Recurrent pregnancy loss (RPL) is defined as the occurrence of two or more consecutive pregnancy losses before 24 weeks of gestation. It affects 3-5% of women who are attempting to conceive. RPL can stem from a variety of causes and is frequently associated with psychological distress and a diminished quality of life. By contrast, recurrent implantation failure (RIF) refers to the inability to achieve a successful pregnancy after three or more high-quality embryo transfers or at least two instances of egg donation. RIF shares several causative factors with RPL. The immunological underpinnings of these conditions involve alterations in uterine NK cells, reductions in M2 macrophages and myeloid-derived suppressor cells, an increased Th1/Th2 ratio, a decreased Treg/Th17 ratio, the presence of shared ≥3 HLA alleles between partners, and autoimmune disorders. Various therapeutic approaches have been employed to address these immunological concerns, achieving varying degrees of success, although some therapies remain contentious within the medical community. This review intends to explore the immunological factors implicated in RPL and RIF and to analyze the immunological treatments employed for these conditions, which may include steroids, intravenous immunoglobulins, calcineurin inhibitors, anti-TNF antibodies, intralipid infusions, granulocyte colony-stimulating factor, and lymphocyte immunotherapy.

Cytokine modulation and immunoregulation of uterine NK cells in pregnancy disorders

Uterine natural killer (uNK) cells play a pivotal role in promoting placental development and supporting maternal-fetal immune tolerance, primarily through cytokine regulation and growth factor production. While the importance of uNK cells in pregnancy is well-established, the mechanisms of their interactions with trophoblasts and contributions to various pregnancy complications remain incompletely understood. This review highlights recent advancements in understanding uNK cell functions, with a focus on cytokine production, growth factor secretion, and receptor-ligand interactions, particularly involving killer immunoglobulin-like receptors (KIR) and human leukocyte antigen-C (HLA-C). We explore how uNK cell dysfunction contributes to pregnancy complications, including preeclampsia, recurrent pregnancy loss, and placenta accreta spectrum (PAS) disorders, emphasizing their roles in immune tolerance and placental health. By detailing the distinct cytokine signaling pathways and functional subtypes of uNK cells, this review provides insights into their regulatory mechanisms essential for pregnancy maintenance. Additionally, we discuss emerging therapeutic strategies targeting uNK-trophoblast interactions and propose future research directions, including the development of non-invasive biomarkers and personalized interventions. This comprehensive review addresses critical knowledge gaps, aiming to advance research in reproductive immunology and guide therapeutic innovations in maternal health.

Immunological Indicators of Recurrent Pregnancy Loss: A Mendelian Randomization Study

Recurrent pregnancy loss (RPL) is thought to be related to maternal-fetal immune tolerance disorders. Immune monitoring of RPL patients mainly involves two aspects: inflammatory factors and immune cells. However, most observational studies have reported controversial findings. This study aimed to confirm whether abnormal inflammatory factors and immune cells in peripheral blood may lead to RPL, and guide clinical immune monitoring. We demonstrated causality using two-sample Mendelian randomization. Sensitivity analysis, reverse Mendelian randomization and meta-analysis were used to enhance the effectiveness of the results. There was a causal relationship between the level of IL-12 (OR = 1.78, 95% CI = 1.25-2.55; P = 0.00149) and RPL for 41 inflammatory factors. We screened 5 groups of immune cell subtypes that were causally associated with RPL: switched memory B-cell absolute count (OR = 0.66, 95% CI = 0.49-0.87, P = 0.00406), IgD + CD24 + B-cell absolute count (OR = 0.69, 95% CI = 0.53-0.88, P = 0.00319), CD39 + resting CD4 regulatory T-cell %CD4 regulatory T-cell (OR = 0.86, 95% CI = 0.78-0.95, P = 0.00252), activated & resting CD4 regulatory T-cell %CD4 regulatory T-cell (OR = 0.89, 95% CI = 0.82-0.97, P = 0.00938) and CD45 RA + CD28-CD8 + T-cell %CD8 + T-cell (OR = 0.99, 95% CI = 0.98-1.00, P = 0.01231). In terms of inflammatory factors, a causal relationship between IL-12 and RPL in peripheral blood was confirmed. We also identified five immune cell phenotypes that play a protective role. This suggests that there may be protective B cells and CD8 + T-cell subsets in peripheral blood, and the protective effect of Tregs was proved again. Immune monitoring of peripheral blood in patients with RPL seems to be necessary and the foundation for precision medicine.

Hydroxychloroquine in recurrent pregnancy loss: data from a French prospective multicenter registry

STUDY QUESTION

What are the outcomes of pregnancies exposed to hydroxychloroquine (HCQ) in women with a history of recurrent pregnancy loss (RPL), and what factors predict the course of these pregnancies beyond the first trimester?

SUMMARY ANSWER

In our cohort of pregnancies in women with a history of RPL exposed to HCQ early in pregnancy, we found that the only factor determining the success of these pregnancies was the number of previous miscarriages.

WHAT IS KNOWN ALREADY

Dysregulation of the maternal immune system plays a role in RPL. HCQ, with its dual immunomodulating and vascular protective effects, is a potential treatment for unexplained RPL.

STUDY DESIGN, SIZE, DURATION

The FALCO (Facteurs de récidive précoce des fausses couches) registry is an ongoing French multicenter infertility registry established in 2017 that includes women (aged from 18 to 49 years) with a history of spontaneous RPL (at least three early miscarriages (≤12 weeks of gestation (WG)) recruited from several university hospitals.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Spontaneous pregnancies enrolled in the FALCO registry with an exposure to HCQ (before conception or at the start of pregnancy) were included. Pregnancies concomitantly exposed to tumor necrosis factor inhibitors, interleukin-1 and -2 inhibitors, intravenous immunoglobulin, and/or intravenous intralipid infusion, were excluded. Concomitant treatment with low-dose aspirin (LDA), low-molecular weight heparin (LMWH), progesterone, and/or prednisone was allowed. All patients underwent the recommended evaluations for investigating RPL. Those who became pregnant received obstetric care in accordance with French recommendations and were followed prospectively. The main endpoint was the occurrence of a pregnancy continuing beyond 12 WG, and the secondary endpoint was the occurrence of a live birth.

MAIN RESULTS AND THE ROLE OF CHANCE

One hundred pregnancies with HCQ exposure in 74 women were assessed. The mean age of the women was 34.2 years, and the median number of previous miscarriages was 5. Concomitant exposure was reported in 78 (78%) pregnancies for prednisone, 56 (56%) pregnancies for LDA, and 41 (41%) pregnancies for LMWH. Sixty-two (62%) pregnancies ended within 12 WG, the other 38 (38%) continuing beyond 12 WG. The risk of experiencing an additional early spontaneous miscarriage increased with the number of previous miscarriages, but not with age. The distributions of anomalies identified in RPL investigations and of exposure to other drugs were similar between pregnancies lasting ≤12 WG and those continuing beyond 12WG. The incidence of pregnancies progressing beyond 12 WG was not higher among pregnancies with at least one positive autoantibody (Ab) (i.e. antinuclear Ab titer ≥1:160, ≥1 positive conventional and/or non-conventional antiphospholipid Ab, and/or positive results for ≥1 antithyroid Ab) without diminished ovarian reserve (18/51, 35.3%) than among those without such autoantibody (18/45, 40.0%) (P = 0.63). Multivariate analysis showed that having ≤4 prior miscarriages was the only factor significantly predictive for achieving a pregnancy > 12 WG, after adjustment for age and duration of HCQ use prior to conception (adjusted odds ratio (OR) = 3.13 [1.31-7.83], P = 0.01).

LIMITATIONS, REASONS FOR CAUTION

Our study has limitations, including the absence of a control group, incomplete data for the diagnostic procedure for RPL in some patients, and the unavailability of results from endometrial biopsies, as well as information about paternal age and behavioral factors. Consequently, not all potential confounding factors could be considered.

WIDER IMPLICATIONS OF THE FINDINGS

Exposure to HCQ in early pregnancy for women with a history of RPL does not seem to prevent further miscarriages, suggesting limited impact on mechanisms related to the maternal immune system.

STUDY FUNDING/COMPETING INTEREST(S)

The research received no specific funding, and the authors declare no competing interests.

TRIAL REGISTRATION NUMBER

clinicaltrial.gov NCT05557201.

Perspective Exploring Novel Associations of IL-18 Levels as a Mediator of the Causal Links between Major Depression and Reproductive Health

This research has suggested a link between major depressive disorder (MDD) and infertility, with interleukin-18 (IL-18) being proposed as a potential mediator due to its connections to both conditions. A Mendelian randomization (MR) approach was utilized in this study, which drew on genetic data from 500,199 European participants studied for MDD, along with additional IL-18 and reproductive health data from the FinnGen consortium and GWAS datasets. Single nucleotide polymorphisms were employed as instrumental variables to examine the causal relationships between MDD, genetically predicted IL-18 levels, and infertility. In our study, bidirectional MR analysis revealed a significant inverse causal relationship between MDD and genetically predicted IL-18 levels, with a higher genetic predisposition to MDD, correlating with reduced IL-18 levels (β: -0.40; 95% confidence interval (CI): -0.69 to -0.11; P = 7.09 × 10-3). Additionally, MDD is found to significantly increase the risk of female infertility. Notably, genetically predicted IL-18 levels demonstrated a protective effect against female infertility (odds ratio (OR): 0.92; 95% CI: 0.86-0.98; P = 1.17 × 10-2). Mediation analysis indicated that genetically predicted IL-18 levels partially mediated the impact of MDD on female infertility associated with cervical, vaginal, other or unspecified origin, accounting for up to 14.61% of this effect. No evidence of pleiotropy or heterogeneity was detected. The role of genetic predispositions to MDD in influencing genetically predicted IL-18 levels, and subsequently, female infertility, was highlighted by our study, offering insights into the complex interplay between mental health and reproductive biology. These findings contribute to a deeper understanding of the genetic and molecular pathways influencing these conditions, suggesting new directions for research and potential therapeutic interventions.

Diabetes Mellitus and Gynecological and Inflammation Disorders Increased the Risk of Pregnancy Loss in a Population Study

(1) Background: Diabetes mellitus (DM) induces oxidative stress and inflammation with negative effect on pregnancy outcomes. This study aimed to determine whether DM increases the risk of pregnancy loss and to identify other potential risk factors; (2) Methods: We identified female patients diagnosed with DM from 2000-2015 in the Taiwanese National Health Insurance Research Database according to the International Classification of Diseases, Ninth Edition, Clinical Modification (ICD-9 CM) code 250. The event was pregnancy loss, defined as ICD-9 CM codes 630-639, which was tracked until 31 December 2015. The control group included 4-fold more non-DM female patients who were matched for age and disease severity. Multivariate Cox regression was employed to determine the risk factors associated with pregnancy loss; (3) Results: The hazard ratio (HR) for the risk of pregnancy loss due to DM was 1.407 (95% confidence interval: 1.099-1.801, p = 0.007), and the risk factors for older age, gynecological disorders and inflammation disorders were included. (4) Conclusions: The study concluded that women with DM have a greater risk of experiencing pregnancy loss. Healthcare providers should proactively manage and educate diabetic patients to reduce their risk of pregnancy loss. Understanding other probable risk factors can help in developing targeted interventions and support systems for women to improve pregnancy outcomes.

Preterm birth, a consequence of immune deviation mediated hyperinflammation

Preterm birth represents a multifaceted syndrome with intricacies still present in our comprehension of its etiology. In the context of a semi-allograft, the prosperity from implantation to pregnancy to delivery hinges on the establishment of a favorable maternal-fetal immune microenvironment and a successful trilogy of immune activation, immune tolerance and then immune activation transitions. The occurrence of spontaneous preterm birth could be related to abnormalities within the immune trilogy, stemming from deviation in maternal and fetal immunity. These immune deviations, characterized by insufficient immune tolerance and early immune activation, ultimately culminated in an unsustainable pregnancy. In this review, we accentuated the role of both innate and adaptive immune reason in promoting spontaneous preterm birth, reviewed the risk of preterm birth from vaginal microbiome mediated by immune changes and the potential of vaginal microbiomes and metabolites as a new predictive marker, and discuss the changes in the role of progesterone and its interaction with immune cells in a preterm birth population. Our objective was to contribute to the growing body of knowledge in the field, shedding light on the immunologic reason of spontaneous preterm birth and effective biomarkers for early prediction, providing a roadmap for forthcoming investigations.

CD24+ decidual stromal cells: a novel heterogeneous population with impaired regulatory T cell induction and potential association with recurrent miscarriage

OBJECTIVE

To explore the heterogeneity of CD24+ decidual stromal cells (DSCs) in patients with recurrent miscarriages (RMs).

DESIGN

We have discerned that the expression of CD24 serves to differentiate two stable and functionally distinct lineages of DSCs. The heterogeneity of CD24+ DSCs has been scrutinized, encompassing variances in stromal markers, transcriptional profiles, metabolic activity, and immune regulation.

SETTING

Department of Reproductive Immunology, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University; Shanghai Institute of Immunity and Infection, Chinese Academy of Science.

PATIENTS

A total of 129 early decidual samples were obtained, comprising 36 from healthy donors and 93 from patients with RMs. Blood samples were collected before the surgical procedure. Paraffin-embedded segments from 20 decidual samples of patients with RMs were obtained.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The flow cytometry was used to quantify the expression of CD24+ DSCs in both healthy donors and patients with RMs, although it also evaluated the cellular heterogeneity. To ascertain the transcriptomic profiles of CD24+ DSCs by reanalyzing our single-cell transcriptomic data. Additionally, to measure the metabolomic activity of CD24+ DSCs from patients with RMs, ultraperformance liquid chromatography-mass spectrometry was employed. Through the implementation of a coculture system, we unraveled the role of CD24+ DSCs in immune regulation.

RESULTS

Patients with RMs exhibit a notable enrichment of CD24+ DSCs, revealing a pronounced heterogeneity characterized by variations in stromal markers and transcriptional profiles. The heightened enrichment of CD24+ DSCs may play a pivotal role in triggering decidual inflammation and dysfunction in decidualization. Furthermore, CD24+ DSCs showed diverse metabolic activities and impeded the induction of naïve CD4+ T cells into regulatory T cells through the abundant secretion of 3-hydroxyisovaleric acid. Finally, our investigations have revealed that intraperitoneal administration of 3-hydroxyisovaleric acid in mouse models can elevate the risk of RM.

CONCLUSION

We have successfully identified a disease-associated subset of CD24+ decidual stromal cells that could potentially contribute to the development of RM through the impairment of decidual immune tolerance. Targeting these specific CD24+ DSCs might hold promising prospects for therapeutic interventions in the clinical management of RM.

A disrupted FOXP3 transcriptional signature underpins systemic regulatory T cell insufficiency in early pregnancy failure

Regulatory T (Treg) cell defects are implicated in disorders of embryo implantation and placental development, but the origins of Treg cell dysfunction are unknown. Here, we comprehensively analyzed the phenotypes and transcriptional profile of peripheral blood Treg cells in individuals with early pregnancy failure (EPF). Compared to fertile subjects, EPF subjects had 32% fewer total Treg cells and 54% fewer CD45RA+CCR7+ naive Treg cells among CD4+ T cells, an altered Treg cell phenotype with reduced transcription factor FOXP3 and suppressive marker CTLA4 expression, and lower Treg:Th1 and Treg:Th17 ratios. RNA sequencing demonstrated an aberrant gene expression profile, with upregulation of pro-inflammatory genes including CSF2, IL4, IL17A, IL21, and IFNG in EPF Treg cells. In silico analysis revealed 25% of the Treg cell dysregulated genes are targets of FOXP3. We conclude that EPF is associated with systemic Treg cell defects arising due to disrupted FOXP3 transcriptional control and loss of lineage fidelity.

Pregnancy-related maternal physiological adaptations and fetal chemical exposure

Prenatal life represents a susceptible window of development during which chemical exposures can permanently alter fetal development, leading to an increased likelihood of disease later in life. Therefore, it is essential to assess exposure in the fetus. However, direct assessment in human fetuses is challenging, so most research measures maternal exposure. Pregnancy induces a range of significant physiological changes in women that may affect chemical metabolism and responses. Moreover, placental function, fetal sex, and pregnancy complications may further modify these exposures. The purpose of this narrative review is to give an overview of major pregnancy-related physiological changes, including placental function and impacts of pregnancy complications, to summarize existing studies assessing chemical exposure in human fetal organs, and to discuss possible interactions between physiological changes and exposures. Our review reveals major knowledge gaps in factors affecting fetal chemical exposure, highlighting the need to develop more sophisticated tools for chemical health risk assessment in fetuses.