Transplacental migration of maternal natural killer and T cells assessed by ex vivo human placenta perfusion

INTRODUCTION

The transplacental passage of cells between a mother and her fetus, known as microchimerism, is a less studied process during pregnancy. The frequency of maternal microchimeric cells in fetal tissues in physiological pregnancies and mechanisms responsible for transplacental cell trafficking are poorly understood. This study aimed to evaluate the placental trafficking of maternal peripheral blood mononuclear cells (PBMC) using human ex vivo placenta perfusion.

METHODS

Ten placentas and maternal PBMC were obtained after healthy pregnancies. Flow cytometry was used to characterize PBMC subtypes. They showed a higher percentage of CD3+ T cells compared to CD56+ NK cells. The isolated PBMC were stained with a fluorescent dye and perfused through the maternal circuit of the placenta in an ex vivo perfusion system. Subsequent immunofluorescence staining for CD3+ T cells and CD56+ NK cells was performed on placental tissue sections, and the number of detectable PBMC in different tissue areas was counted using fluorescence microscopy.

RESULTS

The applied method allowed discrimination of perfused autologous maternal cells from cells resident in the placenta before perfusion. Further, it allows additional immunohistochemical labelling and distinction of immune cell subsets. Perfused PBMC were detected in all analyzed placentas, mostly in contact to the syncytiotrophoblast. CD3+ T cells were identified more frequently than CD56+ NK cells and some CD3+ T cells were found inside fetoplacental tissues and vasculature. The results indicate that also other PBMCs than T or NK cells adhere to or enter villous tissue, but they have not been specified in this analysis.

DISCUSSION

Previous studies have detected maternal cells in the fetal circulation which we could mimick in our ex vivo placenta perfusion experiments with fluorescence labelled autologous maternal PBMC. The applied experimental settings did not allow comparison of transmigration abilities of PBMC subsets, but slight modifications of the model will permit further studies of cell transfer processes and microchimerism in pregnancy.

miRNAs associated with endoplasmic reticulum stress and unfolded protein response during decidualization

RESEARCH QUESTION

Do microRNAs (miRNAs) play a role in regulating endoplasmic reticulum stress (ERS) and unfolded protein response (UPR) in decidualized cells and endometrium associated with reproductive failures?

DESIGN

Endometrial stromal cell line St-T1b was decidualized in vitro with 8-Br-cAMP over 5 days, or treated with the ERS inducer thapsigargin. Expression of ERS sensors, UPR markers and potential miRNA regulators was analysed by quantitative PCR. Endometrial biopsies from patients with recurrent pregnancy loss (RPL) and recurrent implantation failure (RIF) were investigated for the location of miRNA expression.

RESULTS

Decidualization of St-T1b cells resulted in increased expression of ERS sensors including ATF6α, PERK and IRE1α, and the UPR marker, CHOP. TXNIP, which serves as a link between the ERS pathway and inflammation, as well as inflammasome NLRP3 and interleukin 1β expression increased in decidualized cells. An in-silico analysis identified miR-17-5p, miR-21-5p and miR-193b-3p as miRNAs potentially involved in regulation of the ERS/UPR pathways and inflammation associated with embryo implantation. Their expression decreased significantly (P ≤ 0.0391) in non-decidualized cells in the presence of thapsigargin. Finally, expression of the selected miRNAs was localized by in-situ hybridization in stromal and glandular epithelial cells in endometrial samples from patients with RPL and RIF. Expression in stroma cells from patients with RPL was lower in comparison with stroma cells from patients with RIF.

CONCLUSIONS

Decidualization in St-T1b cells is accompanied by ERS/UPR processes, associated with an inflammatory response that is potentially influenced by miR-17-5p, miR-21-5p and miR-193b-3p. These miRNAs are expressed differentially in stromal cells from patients with RPL and RIF, indicating an alteration in regulation of the ERS/UPR pathways.

ESMO Expert Consensus Statements on the management of breast cancer during pregnancy (PrBC)

The management of breast cancer during pregnancy (PrBC) is a relatively rare indication and an area where no or little evidence is available since randomized controlled trials cannot be conducted. In general, advances related to breast cancer (BC) treatment outside pregnancy cannot always be translated to PrBC, because both the interests of the mother and of the unborn should be considered. Evidence remains limited and/or conflicting in some specific areas where the optimal approach remains controversial. In 2022, the European Society for Medical Oncology (ESMO) held a virtual consensus-building process on this topic to gain insights from a multidisciplinary group of experts and develop statements on controversial topics that cannot be adequately addressed in the current evidence-based ESMO Clinical Practice Guideline. The aim of this consensus-building process was to discuss controversial issues relating to the management of patients with PrBC. The virtual meeting included a multidisciplinary panel of 24 leading experts from 13 countries and was chaired by S. Loibl and F. Amant. All experts were allocated to one of four different working groups. Each working group covered a specific subject area with two chairs appointed: Planning, preparation and execution of the consensus process was conducted according to the ESMO standard operating procedures.

Characterization of a human placental clearance system to regulate serotonin levels in the fetoplacental unit

BACKGROUND

Serotonin (5-HT) is a biogenic monoamine with diverse functions in multiple human organs and tissues. During pregnancy, tightly regulated levels of 5-HT in the fetoplacental unit are critical for proper placental functions, fetal development, and programming. Despite being a non-neuronal organ, the placenta expresses a suite of homeostatic proteins, membrane transporters and metabolizing enzymes, to regulate monoamine levels. We hypothesized that placental 5-HT clearance is important for maintaining 5-HT levels in the fetoplacental unit. We therefore investigated placental 5-HT uptake from the umbilical circulation at physiological and supraphysiological levels as well as placental metabolism of 5-HT to 5-hydroxyindoleacetic acid (5-HIAA) and 5-HIAA efflux from trophoblast cells.

METHODS

We employed a systematic approach using advanced organ-, tissue-, and cellular-level models of the human placenta to investigate the transport and metabolism of 5-HT in the fetoplacental unit. Human placentas from uncomplicated term pregnancies were used for perfusion studies, culturing explants, and isolating primary trophoblast cells.

RESULTS

Using the dually perfused placenta, we observed a high and concentration-dependent placental extraction of 5-HT from the fetal circulation. Subsequently, within the placenta, 5-HT was metabolized to 5-hydroxyindoleacetic acid (5-HIAA), which was then unidirectionally excreted to the maternal circulation. In the explant cultures and primary trophoblast cells, we show concentration- and inhibitor-dependent 5-HT uptake and metabolism and subsequent 5-HIAA release into the media. Droplet digital PCR revealed that the dominant gene in all models was MAO-A, supporting the crucial role of 5-HT metabolism in placental 5-HT clearance.

CONCLUSIONS

Taken together, we present transcriptional and functional evidence that the human placenta has an efficient 5-HT clearance system involving (1) removal of 5-HT from the fetal circulation by OCT3, (2) metabolism to 5-HIAA by MAO-A, and (3) selective 5-HIAA excretion to the maternal circulation via the MRP2 transporter. This synchronized mechanism is critical for regulating 5-HT in the fetoplacental unit; however, it can be compromised by external insults such as antidepressant drugs.

Host-pathogen interactions mediated by extracellular vesicles in Toxoplasma gondii infection during pregnancy

Molecular communication between a pathogen and its host is crucial for a successful interplay. Extracellular vesicles (EVs) act as mediators for the delivery of molecular signals among pathogens or between pathogens and the host. Toxoplasma gondii (T. gondii), an intracellular parasite with a worldwide presence, produces EVs itself, or induces the secretion of EVs from infected host cells potentially having capacities to modulate the host immune response. T. gondii infection is particularly important during pregnancy. Depending on the gestational age at the time of infection, the parasite can be transmitted through the placenta to the fetus, causing clinical complications such as jaundice, hepatosplenomegaly, chorioretinitis, cranioencephalic abnormalities, or even death. T. gondii infection is related to a pro-inflammatory immune response in both mother and fetus, which may enhance parasite transmission, but the implication of EV signaling in this process remains unclear. In this review, we summarize the current knowledge on EV release from T. gondii and its human host cells in regard to the immunological consequences and the passage through the placenta.

Identification of altered miRNAs and their targets in placenta accreta

Placenta accreta spectrum (PAS) is one of the major causes of maternal morbidity and mortality worldwide with increasing incidence. PAS refers to a group of pathological conditions ranging from the abnormal attachment of the placenta to the uterus wall to its perforation and, in extreme cases, invasion into surrounding organs. Among them, placenta accreta is characterized by a direct adhesion of the villi to the myometrium without invasion and remains the most common diagnosis of PAS. Here, we identify the potential regulatory miRNA and target networks contributing to placenta accreta development. Using small RNA-Seq followed by RT-PCR confirmation, altered miRNA expression, including that of members of placenta-specific miRNA clusters (e.g., C19MC and C14MC), was identified in placenta accreta samples compared to normal placental tissues. In situ hybridization (ISH) revealed expression of altered miRNAs mostly in trophoblast but also in endothelial cells and this profile was similar among all evaluated degrees of PAS. Kyoto encyclopedia of genes and genomes (KEGG) analyses showed enriched pathways dysregulated in PAS associated with cell cycle regulation, inflammation, and invasion. mRNAs of genes associated with cell cycle and inflammation were downregulated in PAS. At the protein level, NF-κB was upregulated while PTEN was downregulated in placenta accreta tissue. The identified miRNAs and their targets are associated with signaling pathways relevant to controlling trophoblast function. Therefore, this study provides miRNA:mRNA associations that could be useful for understanding PAS onset and progression.

Human-Based New Approach Methodologies in Developmental Toxicity Testing: A Step Ahead from the State of the Art with a Feto-Placental Organ-on-Chip Platform

Developmental toxicity testing urgently requires the implementation of human-relevant new approach methodologies (NAMs) that better recapitulate the peculiar nature of human physiology during pregnancy, especially the placenta and the maternal/fetal interface, which represent a key stage for human lifelong health. Fit-for-purpose NAMs for the placental-fetal interface are desirable to improve the biological knowledge of environmental exposure at the molecular level and to reduce the high cost, time and ethical impact of animal studies. This article reviews the state of the art on the available in vitro (placental, fetal and amniotic cell-based systems) and in silico NAMs of human relevance for developmental toxicity testing purposes; in addition, we considered available Adverse Outcome Pathways related to developmental toxicity. The OECD TG 414 for the identification and assessment of deleterious effects of prenatal exposure to chemicals on developing organisms will be discussed to delineate the regulatory context and to better debate what is missing and needed in the context of the Developmental Origins of Health and Disease hypothesis to significantly improve this sector. Starting from this analysis, the development of a novel human feto-placental organ-on-chip platform will be introduced as an innovative future alternative tool for developmental toxicity testing, considering possible implementation and validation strategies to overcome the limitation of the current animal studies and NAMs available in regulatory toxicology and in the biomedical field.

Ex vivo dual perfusion of an isolated human placenta cotyledon: Towards protocol standardization and improved inter-centre comparability

Since the full development of the ex vivo dual perfusion model of the human placenta cotyledon, the technique has provided essential insight into how nutrients, lipids, gases, immunoglobulins, endocrine agents, pharmaceuticals, chemicals, nanoparticles, micro-organisms and parasites might traverse the maternofetal barrier. Additionally, the model has been instrumental in gaining a better understanding of the regulation of vascular tone, endocrinology and metabolism within this organ. The human placenta is unique amongst species in its anatomy and transfer modalities. This orthologous diversity therefore requires an appropriate consideration of placental transfer rates of compounds, particles and micro-organisms specific to humans. Different research centres have adapted this model with a wide variation in perfusion parameters, including in the establishment of perfusion, perfusate composition, gassing regime, cannulation method, flow rates, perfused tissue mass, and also in the application of quality control measures. The requirement to harmonise and standardise perfusion practice between centres is largely driven by the need to obtain consistency in our understanding of placental function, but also in the qualification of the model for acceptance by regulatory agencies in drug and toxicology testing. A pilot study is proposed, aiming to describe how existing inter-centre variation in perfusion methodology affects placental metabolism, protein synthesis, oxygen consumption, the materno-fetal transfer of key molecular markers, and placental structure.

Synergies of Extracellular Vesicles and Microchimerism in Promoting Immunotolerance During Pregnancy

The concept of biological identity has been traditionally a central issue in immunology. The assumption that entities foreign to a specific organism should be rejected by its immune system, while self-entities do not trigger an immune response is challenged by the expanded immunotolerance observed in pregnancy. To explain this "immunological paradox", as it was first called by Sir Peter Medawar, several mechanisms have been described in the last decades. Among them, the intentional transfer and retention of small amounts of cells between a mother and her child have gained back attention. These microchimeric cells contribute to expanding allotolerance in both organisms and enhancing genetic fitness, but they could also provoke aberrant alloimmune activation. Understanding the mechanisms used by microchimeric cells to exert their function in pregnancy has proven to be challenging as per definition they are extremely rare. Profiting from studies in the field of transplantation and cancer research, a synergistic effect of microchimerism and cellular communication based on the secretion of extracellular vesicles (EVs) has begun to be unveiled. EVs are already known to play a pivotal role in feto-maternal tolerance by transferring cargo from fetal to maternal immune cells to reshape their function. A further aspect of EVs is their function in antigen presentation either directly or on the surface of recipient cells. Here, we review the current understanding of microchimerism in the feto-maternal tolerance during human pregnancy and the potential role of EVs in mediating the allorecognition and tropism of microchimeric cells.

Emerging Concepts in Innate Lymphoid Cells, Memory, and Reproduction

Members of the innate immune system, innate lymphoid cells (ILCs), encompass five major populations (Natural Killer (NK) cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue inducer cells) whose functions include defense against pathogens, surveillance of tumorigenesis, and regulation of tissue homeostasis and remodeling. ILCs are present in the uterine environment of humans and mice and are dynamically regulated during the reproductive cycle and pregnancy. These cells have been repurposed to support pregnancy promoting maternal immune tolerance and placental development. To accomplish their tasks, immune cells employ several cellular and molecular mechanisms. They have the capacity to remember a previously encountered antigen and mount a more effective response to succeeding events. Memory responses are not an exclusive feature of the adaptive immune system, but also occur in innate immune cells. Innate immune memory has already been demonstrated in monocytes/macrophages, neutrophils, dendritic cells, and ILCs. A population of decidual NK cells characterized by elevated expression of NKG2C and LILRB1 as well as a distinctive transcriptional and epigenetic profile was found to expand during subsequent pregnancies in humans. These cells secrete high amounts of interferon-γ and vascular endothelial growth factor likely favoring placentation. Similarly, uterine ILC1s in mice upregulate CXCR6 and expand in second pregnancies. These data provide evidence on the development of immunological memory of pregnancy. In this article, the characteristics, functions, and localization of ILCs are reviewed, emphasizing available data on the uterine environment. Following, the concept of innate immune memory and its mechanisms, which include epigenetic changes and metabolic rewiring, are presented. Finally, the emerging role of innate immune memory on reproduction is discussed. Advances in the comprehension of ILC functions and innate immune memory may contribute to uncovering the immunological mechanisms underlying female fertility/infertility, placental development, and distinct outcomes in second pregnancies related to higher birth weight and lower incidence of complications.

MatriGrid® Based Biological Morphologies: Tools for 3D Cell Culturing

Recent trends in 3D cell culturing has placed organotypic tissue models at another level. Now, not only is the microenvironment at the cynosure of this research, but rather, microscopic geometrical parameters are also decisive for mimicking a tissue model. Over the years, technologies such as micromachining, 3D printing, and hydrogels are making the foundation of this field. However, mimicking the topography of a particular tissue-relevant substrate can be achieved relatively simply with so-called template or morphology transfer techniques. Over the last 15 years, in one such research venture, we have been investigating a micro thermoforming technique as a facile tool for generating bioinspired topographies. We call them MatriGrid^®s. In this research account, we summarize our learning outcome from this technique in terms of the influence of 3D micro morphologies on different cell cultures that we have tested in our laboratory. An integral part of this research is the evolution of unavoidable aspects such as possible label-free sensing and fluidic automatization. The development in the research field is also documented in this account.

Splenic B1 B Cells Acquire a Proliferative and Anti-Inflamatory Profile During Pregnancy in Mice

B cells are a heterogeneous cell population with differential ontogeny, anatomical location, and functions. B1 B cells are a distinct subpopulation characterized by their unique capacity of self-renewal, the production of large quantities of IL-10, and the ability to secrete protective, anti-inflammatory natural antibodies (NAbs), presumably upon down-regulation of CD1d expression. Although natural antibodies are thought to be protective, due to their polyreactivity, their participation in certain autoimmune diseases has been suggested. In the context of pregnancy, the role of B1 B cells has been discussed controversially. While in human pregnancies B1 B cells and natural/polyreactive antibodies they produce are involved in the development of preeclampsia, in mice they promote healthy gestation and fetal protection. In this work, we aimed to functionally characterize the splenic B1 B cell population during pregnancy in mice. Functional enrichment analysis using only up-regulated transcripts from a transcriptomic profile performed on total splenic B cells from pregnant compared to non-pregnant mice showed augmented cell cycle and DNA replication pathways. Proliferation studies by flow cytometry showed augmented Ki-67 proliferation marker expression and percentages of B1 B cells. Furthermore, B1 B cells produced higher levels of IL-10 and lower levels of TNF-α leading to an increased IL-10/TNF-α ratio and showing an immunoregulatory phenotype. Finally, we observed lower expression of CD1d on B1 B cells, suggesting a higher capacity to produce NAbs in the context of pregnancy. In summary, our results showed not only an expanded and proliferative splenic B1 B cell population during pregnancy but also the acquisition of immunomodulatory capacities suggesting its critical role in the intricate process of pregnancy tolerance.

The Role of Non-Coding RNAs in the Human Placenta

Non-coding RNAs (ncRNAs) play a central and regulatory role in almost all cells, organs, and species, which has been broadly recognized since the human ENCODE project and several other genome projects. Nevertheless, a small fraction of ncRNAs have been identified, and in the placenta they have been investigated very marginally. To date, most examples of ncRNAs which have been identified to be specific for fetal tissues, including placenta, are members of the group of microRNAs (miRNAs). Due to their quantity, it can be expected that the fairly larger group of other ncRNAs exerts far stronger effects than miRNAs. The syncytiotrophoblast of fetal origin forms the interface between fetus and mother, and releases permanently extracellular vesicles (EVs) into the maternal circulation which contain fetal proteins and RNA, including ncRNA, for communication with neighboring and distant maternal cells. Disorders of ncRNA in placental tissue, especially in trophoblast cells, and in EVs seem to be involved in pregnancy disorders, potentially as a cause or consequence. This review summarizes the current knowledge on placental ncRNA, their transport in EVs, and their involvement and pregnancy pathologies, as well as their potential for novel diagnostic tools.

The fate of human SUSD2+ endometrial mesenchymal stem cells during decidualization

Regeneration of the endometrial stromal compartment in premenopausal women is likely maintained by the perivascular endometrial mesenchymal stem/stromal cells (eMSC) expressing sushi domain containing 2 (SUSD2). The fate of SUSD2+ eMSC during pregnancy and their role in decidualization is not fully known. The aim of our study was to determine the effect of progesterone on the stemness of the SUSD2+ eMSC isolated from non-pregnant uterine samples. Secondary objectives were to characterize the functional capacity including differentiation and clonogenicity assays of SUSD2+ eMSC isolated from decidua at full term and compare it to the capacity of those isolated from non-pregnant uterine samples. Progesterone treatment induced changes in the decidual gene expression profile in non-pregnant SUSD2+ eMSC. Data analysis of a publicly available single cell RNA-seq data set revealed differential expression of several mesenchymal and epithelial signature genes between the SUSD2+ eMSC and the decidual stromal cells, suggesting mesenchymal-to-epithelial transition occurs during decidualization. Histological analysis revealed a significantly lower abundance of SUSD2+ eMSC in 1st trimester and full term samples compared to non-pregnant samples, p = 0.0296 and 0.005, respectively. The differentiation and the colony forming capacity did not differ significantly between the cells isolated from non-pregnant and pregnant uterine samples. Our results suggest that SUSD2+ eMSC undergo decidualization in vitro, while maintaining MSC plasma membrane phenotype. Human eMSC seem to play an important role in the course of endometrial decidualization and embryo implantation. Pregnancy reduced the abundance of SUSD2+ eMSC, however eMSC function remains intact.

Overview of Drug Transporters in Human Placenta

The transport of drugs across the placenta is a point of great importance in pharmacotherapy during pregnancy. However, the knowledge of drug transport in pregnancy is mostly based on experimental clinical data, and the underlying biological mechanisms are not fully understood. In this review, we summarize the current knowledge of drug transporters in the human placenta. We only refer to human data since the placenta demonstrates great diversity among species. In addition, we describe the experimental models that have been used in human placental transport studies and discuss their availability. A better understanding of placental drug transporters will be beneficial for the health of pregnant women who need drug treatment and their fetuses.

Pregnancy and pandemics: Interaction of viral surface proteins and placenta cells

Throughout history, pandemics of infectious diseases caused by emerging viruses have spread worldwide. Evidence from previous outbreaks demonstrated that pregnant women are at high risk of contracting the diseases and suffering from adverse outcomes. However, while some viruses can cause major health complications for the mother and her fetus, others do not appear to affect pregnancy. Viral surface proteins bind to specific receptors on the cellular membrane of host cells and begin therewith the infection process. During pregnancy, the molecular features of these proteins may determine specific target cells in the placenta, which may explain the different outcomes. In this review, we display information on Variola, Influenza, Zika and Corona viruses focused on their surface proteins, effects on pregnancy, and possible target placental cells. This will contribute to understanding viral entry during pregnancy, as well as to develop strategies to decrease the incidence of obstetrical problems in current and future infections.

Addressing microchimerism in pregnancy by ex vivo human placenta perfusion

The physical connection of mother and offspring during pregnancy allows the bi-directional exchange of a small number of cells through the placenta. These cells, which can persist long-term in the recipient individual are genetically foreign to it and therefore fulfill the principle of microchimerism. Over the last years, pioneer research on microchimeric cells revealed their role in immune adaptation during pregnancy and priming of tolerogenic responses in the progeny. However, the mechanisms involved in cell transfer across the placenta barrier remain poorly investigated. In this review, we summarize the evidence of fetomaternal microchimerism, propose a mechanism for cell trafficking through the placenta and discuss the different models and techniques available for its analysis. Likewise, we aim to generate interest in the use of ex vivo placenta perfusion to investigate microchimerism in physiological and pathological settings.

Adverse effects on female fertility from vaccination against COVID-19 unlikely

This opinion paper briefly presents arguments that support the unlikelihood of an impact on female fertility from current covid-19 vaccines.

The road (not) taken - Placental transfer and interspecies differences

Species differences are among the main reasons for the high failure rate of preclinical studies. A better awareness and understanding of these differences might help to improve the outcome of preclinical research. In reproduction, the placenta is the central organ regulating fetal exposure to a substance circulating in the maternal organism. Exact information about placental transfer can help to better estimate the toxic potential of a substance. From an evolutionary point of view, the chorioallantoic placenta is the organ with the highest anatomical diversity among species. Moreover, frequently used animal models in reproduction belong to rodents and lagomorphs, two groups that are characterized by the generation of an additional type of placenta, which is crucial for fetal development, but absent from humans: the inverted yolk sac placenta. Taken together, the translatability of placental transfer studies from laboratory animals to humans is challenging, which is supported by the fact that numerous species-dependent toxic effects are described in literature. Thus, reliable human-relevant data are frequently lacking and the toxic potential of chemicals and pharmaceuticals for humans can hardly be estimated, often resulting in recommendations that medical treatments or exposure to chemicals should be avoided for safety reasons. Although species differences of placental anatomy have been described frequently and the need for human-relevant research models has been emphasized, analyses of substances with species-dependent placental transfer have been performed only sporadically. Here, we present examples for species-specific placental transfer, including that of nanoparticles and pharmaceuticals, and discuss potential underlying mechanisms. With respect to the COVID 19-pandemic it might be of interest that some antiviral drugs are reported to feature species-specific placental transfer. Further, differences in placental structure and antibody transfer may affect placental transfer of ZIKA virus.

Smoking for two- effects of tobacco consumption on placenta

Tobacco smoking is an important public health issue recognized by the world health organization as one of the most serious, preventable risk factors for developing a series of pregnancy pathologies. Maternal smoking is positively associated with intrauterine growth restriction (IUGR) and gestational diabetes (GDM), but negatively associated with preeclampsia (PE). In this review, we examine epidemiological, clinical and laboratory studies of smoking effects on immunoregulation during pregnancy, trophoblast function, and placental vasculature development and metabolism. We aim to identify effects of tobacco smoke components on specific placental compartments or cells, which may contribute to the understanding of the influences of maternal smoking on placenta function in normal and pathological pregnancies. Data corroborates that in any trimester, smoking is unsafe for pregnancy and that its detrimental effects outweigh questionable benefits. The effects of maternal smoking on the maternal immune regulation throughout pregnancy and the impact of different tobacco products on fetal growth have not yet been fully understood. Smoking cessation rather than treatment with replacement therapies is recommended for future mothers because also single components of tobacco and its smoke may have detrimental effects on placental function.