Epidemiology of Pregnancy Complications Through the Lens of Immunological Memory

Memory regulatory T cells in pregnancy

Pregnancy requires the process of maternal immune tolerance to semi-allogeneic embryos. In contrast, an overreactive maternal immune system to embryo-specific antigens is likely to result in the rejection of embryos while damaging the invading placenta, such that the likelihood of adverse pregnancy outcomes can be increased. Regulatory T cells (Tregs) are capable of suppressing excessive immune responses and regulating immune homeostasis. When stimulating Tregs, specific antigens will differentiate into memory Tregs with long-term survival and rapid and powerful immune regulatory ability. Immunomodulatory effects mediated by memory Tregs at the maternal-fetal interface take on critical significance in a successful pregnancy. The impaired function of memory Tregs shows a correlation with various pregnancy complications (e.g., preeclampsia, gestational diabetes mellitus, and recurrent pregnancy losses). However, the differentiation process and characteristics of memory Tregs, especially their role in pregnancy, remain unclear. In this study, a review is presented in terms of memory Tregs differentiation and activation, the characteristics of memory Tregs and their role in pregnancy, and the correlation between memory Tregs and pregnancy complications. Furthermore, several potential therapeutic methods are investigated to restore the function of memory Tregs in accordance with immunopathologies arising from memory Tregs abnormalities and provide novel targets for diagnosing and treating pregnancy-associated diseases.

Reproductive outcomes after pregnancy-induced displacement of preexisting microchimeric cells

Pregnancy confers partner-specific protection against complications in future pregnancy that parallel persistence of fetal microchimeric cells (FMcs) in mothers after parturition. We show that preexisting FMcs become displaced by new FMcs during pregnancy and that FMc tonic stimulation is essential for expansion of protective fetal-specific forkhead box P3 (FOXP3)-positive regulatory T cells (Treg cells). Maternal microchimeric cells and accumulation of Treg cells with noninherited maternal antigen (NIMA) specificity are similarly overturned in daughters after pregnancy, highlighting a fixed microchimeric cell niche. Whereas NIMA-specific tolerance is functionally erased by pregnancy, partner-specific resiliency against pregnancy complications persists in mothers despite paternity changes in intervening pregnancy. Persistent fetal tolerance reflects FOXP3 expression plasticity, which allows mothers to more durably remember their babies, whereas daughters forget their mothers with new pregnancy-imprinted immunological memories.

The Vaginal Microbiota of Pregnant Women Varies with Gestational Age, Maternal Age, and Parity

The composition of the vaginal microbiota is heavily influenced by pregnancy and may factor into pregnancy complications, including spontaneous preterm birth. However, results among studies have been inconsistent due, in part, to variation in sample sizes and ethnicity. Thus, an association between the vaginal microbiota and preterm labor continues to be debated. Yet, before assessing associations between the composition of the vaginal microbiota and preterm labor, a robust and in-depth characterization of the vaginal microbiota throughout pregnancy in the specific study population under investigation is required. Here, we report a large longitudinal study (n = 474 women, 1,862 vaginal samples) of a predominantly African-American cohort-a population that experiences a relatively high rate of pregnancy complications-evaluating associations between individual identity, gestational age, and other maternal characteristics with the composition of the vaginal microbiota throughout gestation resulting in term delivery. The principal factors influencing the composition of the vaginal microbiota in pregnancy are individual identity and gestational age at sampling. Other factors are maternal age, parity, obesity, and self-reported Cannabis use. The general pattern across gestation is for the vaginal microbiota to remain or transition to a state of Lactobacillus dominance. This pattern can be modified by maternal parity and obesity. Regardless, network analyses reveal dynamic associations among specific bacterial taxa within the vaginal ecosystem, which shift throughout the course of pregnancy. This study provides a robust foundational understanding of the vaginal microbiota in pregnancy and sets the stage for further investigation of this microbiota in obstetrical disease. IMPORTANCE There is debate regarding links between the vaginal microbiota and pregnancy complications, especially spontaneous preterm birth. Inconsistencies in results among studies are likely due to differences in sample sizes and cohort ethnicity. Ethnicity is a complicating factor because, although all bacterial taxa commonly inhabiting the vagina are present among all ethnicities, the frequencies of these taxa vary among ethnicities. Therefore, an in-depth characterization of the vaginal microbiota throughout pregnancy in the specific study population under investigation is required prior to evaluating associations between the vaginal microbiota and obstetrical disease. This initial investigation is a large longitudinal study of the vaginal microbiota throughout gestation resulting in a term delivery in a predominantly African-American cohort, a population that experiences disproportionally negative maternal-fetal health outcomes. It establishes the magnitude of associations between maternal characteristics, such as age, parity, body mass index, and self-reported Cannabis use, on the vaginal microbiota in pregnancy.

Multiomic signals associated with maternal epidemiological factors contributing to preterm birth in low- and middle-income countries

Preterm birth (PTB) is the leading cause of death in children under five, yet comprehensive studies are hindered by its multiple complex etiologies. Epidemiological associations between PTB and maternal characteristics have been previously described. This work used multiomic profiling and multivariate modeling to investigate the biological signatures of these characteristics. Maternal covariates were collected during pregnancy from 13,841 pregnant women across five sites. Plasma samples from 231 participants were analyzed to generate proteomic, metabolomic, and lipidomic datasets. Machine learning models showed robust performance for the prediction of PTB (AUROC = 0.70), time-to-delivery (r = 0.65), maternal age (r = 0.59), gravidity (r = 0.56), and BMI (r = 0.81). Time-to-delivery biological correlates included fetal-associated proteins (e.g., ALPP, AFP, and PGF) and immune proteins (e.g., PD-L1, CCL28, and LIFR). Maternal age negatively correlated with collagen COL9A1, gravidity with endothelial NOS and inflammatory chemokine CXCL13, and BMI with leptin and structural protein FABP4. These results provide an integrated view of epidemiological factors associated with PTB and identify biological signatures of clinical covariates affecting this disease.

Maternal vaccination to prevent adverse pregnancy outcomes: An underutilized molecular immunological intervention?

Adverse pregnancy outcomes including maternal mortality, stillbirth, preterm birth, intrauterine growth restriction cause millions of deaths each year. More effective interventions are urgently needed. Maternal immunization could be one such intervention protecting the mother and newborn from infection through its pathogen-specific effects. However, many adverse pregnancy outcomes are not directly linked to the infectious pathogens targeted by existing maternal vaccines but rather are linked to pathological inflammation unfolding during pregnancy. The underlying pathogenesis driving such unfavourable outcomes have only partially been elucidated but appear to relate to altered immune regulation by innate as well as adaptive immune responses, ultimately leading to aberrant maternal immune activation. Maternal immunization, like all immunization, impacts the immune system beyond pathogen-specific immunity. This raises the possibility that maternal vaccination could potentially be utilised as a pathogen-agnostic immune modulatory intervention to redirect abnormal immune trajectories towards a more favourable phenotype providing pregnancy protection. In this review we describe the epidemiological evidence surrounding this hypothesis, along with the mechanistic plausibility and present a possible path forward to accelerate addressing the urgent need of adverse pregnancy outcomes.

Antinuclear antibodies positivity in women in reproductive age: From infertility to adverse obstetrical outcomes - A meta-analysis

This systematic review and meta-analysis were designed to identify possible correlations between isolated serum antinuclear antibody (ANA) and (i) infertility in the context of in-vitro fertilization (IVF), (ii) idiopathic recurrent pregnancy losses (RPL), and (iii) second/ third trimester pregnancy complications. We performed a systematic review and meta-analysis of the literature in PubMed Library database from inception to March 2022 following PRISMA guidelines. Our pooled results showed a lower pregnancy rate among ANA-positive women undergoing IVF/ICSI compared to ANA-negative women undergoing the same procedures (279/908 versus 1136/2347, random effect, odds ratio -OR- 0.50, 95% confidence interval -CI- 0.38-0.67, p 0.00001, I² = 58%). We also reported a higher miscarriage rate among ANA-positive compared to ANA-negative women (48/223 versus 109/999, random effect, OR: 3.25 95% CI: 1.57-6.76, p = 0.002, I² = 61%) and a lower implantation rate (320/1489 versus 1437/4205, random effect, OR: 0.51, 95% CI: 0.36-0.72, p = 0.0001, I² = 78%). Regarding RPL, pooled results demonstrated a higher prevalence of ANA-positivity in RPL women compared to controls (698/2947 versus 240/3145, random effect, OR: 3.22, 95% CI: 2.12-4.88, p 0.00001, I² 77%), either using > 2 or > 3 pregnancy losses threshold for defining RPL. Heterogeneity of reporting outcome did not allow a quantitative analysis and led to no clear demonstration of an effect of serum ANA on the incidence of stillbirth, preeclampsia and hypertensive disorders. In conclusion, the unfavorable effect of serum ANA was observed in women following IVF. Similarly, ANA were associated with the risk of RPL, while data were unconclusive in terms of late pregnancy complications.

The Regulatory-T-Cell Memory Phenotype: What We Know

In immunology, the discovery of regulatory T (Treg) cells was a major breakthrough. Treg cells play a key role in pregnancy maintenance, in the prevention of autoimmune responses, and in the control of all immune responses, including responses to self cells, cancer, infection, and a transplant. It is currently unclear whether Treg cells are capable of long-term memory of an encounter with an antigen. Although the term “immunological memory” usually means an enhanced ability to protect the body from reinfection, the memory of the suppressive activity of Treg cells helps to avoid the state of generalized immunosuppression that may result from the second activation of the immune system. In this review, we would like to discuss the concept of regulatory memory and in which tissues memory Treg cells can perform their functions.

Effect of hypertensive disorders of pregnancy on peripheral venous blood cell count in preterm infants with a gestational age of 28-34 weeks

OBJECTIVES

To study the effect of hypertensive disorders of pregnancy on peripheral venous blood cell count in preterm infants with a gestational age of 28-34 weeks.

METHODS

A total of 227 preterm infants with a gestational age of 28-34 weeks who were admitted to the Department of Pediatrics, the First Hospital Affiliated to Kunming Medical University, from January to December 2020, and whose mothers had hypertensive disorders of pregnancy were enrolled as the study group. A total of 227 preterm infants with a gestational age of 28-34 weeks who were admitted during the same period and whose mothers did not have hypertensive disorders of pregnancy were enrolled as the control group. According to maternal blood pressure during pregnancy, the study group was divided into three subgroups: gestational hypertension (n=75), mild preeclampsia (n=81), and severe preeclampsia (n=71). According to the birth weight of the preterm infants, the study group was divided into two subgroups: small for gestational age (SGA) (n=113) and appropriate for gestational age (AGA) (n=114). Peripheral blood cell count on day 1 after birth was compared between the study and control groups, as well as between the subgroups of the study group.

RESULTS

Compared with the control group, the study group had significantly lower white blood cell count, absolute neutrophil count, and blood platelet count (P<0.05) and significantly higher incidence rates of leucopenia and neutropenia (P<0.05). The subgroup analysis showed that the mild preeclampsia and severe preeclampsia subgroups had significantly lower white blood cell count, absolute neutrophil count, and blood platelet count than the gestational hypertension subgroup (P<0.05), and that the SGA subgroup had significantly lower white blood cell count, absolute neutrophil count, and blood platelet count than the AGA subgroup (P<0.05).

CONCLUSIONS

Hypertensive disorders of pregnancy can affect the peripheral venous blood cell count of preterm infants, which is more significant in infants with maternal preeclampsia and SGA infants.