Introduction

Volatile organic compounds (VOCs) are compounds containing at least one carbon atom and one or more other elements, such as hydrogen, oxygen, or nitrogen. In addition, these compounds are characterized by their high volatility, switching easily from liquid to gaseous states under normal conditions of pressure and temperature. Their negative effects on health have been extensively studied and depend on the nature of the exposure: acute or chronic, and single or combined. Acute exposure to VOCs usually induces irritation of the respiratory tract, skin, and eyes (Takahashi et al. 2007) and damage to the central nervous system (Neubert 2001), which are usually transient. Exposure to low concentrations of VOCs over a long period can affect the body with carcinogenic effects (Yin et al. 1996) and alterations in reproductive functions (Luderer et al. 2004) in fetal development (Hooiveld 2006). In addition, the negative effects of these molecules on health are almost more significant if exposure occurs early in life. Therefore, exposure to VOCs during the fetal period (1) may induce an increased risk of low birth weight (Ghosh et al. 2013; Miller et al. 2020) and preterm birth (Santos and Nascimento 2019; Cassidy-Bushrow et al. 2020; Miller et al. 2020), (2) may adversely affect early postnatal growth (Chang et al. 2017) and neurobehavioural development in the early life stage (Chang et al. 2018; Nakaoka et al. 2021), and (3) may be related to wheezing in early infancy (Franck et al. 2014). Benzene, toluene, and ethylbenzene are the VOCs most frequently linked with adverse birth outcomes, probably because these compounds are the most studied since they are recognized environmental pollutants (Zhou et al. 2023) with well-described toxic properties (mutagenic, carcinogenic, reprotoxic). In addition, they may have negative impacts on maternal health through oxidative stress (Chen et al. 2023), inflammation (Cassidy-Bushrow et al. 2021), and epigenetic change (Yusoff et al. 2023).

Approximately 3000 different VOCs have been detected in expired human air. They have been detected in urine, blood (Miekisch et al. 2001), stool (Frau et al. 2021), and saliva, but it is in breath (Amann et al. 2014) that these compounds have been extensively studied. Most of these samples contained more than 200 VOCs. Their origins may be endogenous or exogenous. VOCs with endogenous origins may result from intestinal bacterial activity (Bone et al. 1976; Cope et al. 2000) or metabolic processes, such as protein oxidation by fecal flora (Miekisch et al. 2004), sulfur amino acid degradation (Scislowski and Pickard 1994; Luo et al. 2011), or sugar catabolism (i.e. the Embden–Meyerhof–Parnas pathway and lactic fermentation) (Miller and Wolin 1979). In addition, studies investigating the chemical composition of exhaled air from patients with various diseases have provided useful insights into the metabolic processes that produce endogenous VOCs. Breath alkane (pentane) output is a good index of lipid peroxidation (Kohlmuller and Kochen 1993; Mendis et al. 1995; Shin et al. 1997; Aghdassi and Allard 2000; Miekisch et al. 2001, 2004); sulfur-containing compounds are considered markers of liver impairment (Scislowski and Pickard 1994); change in isoprene concentration has been related to cholesterol metabolism (Karl et al. 2001); a high level of acetone is a long-recognized and useful marker of uncontrolled diabetes mellitus (Lebovitz 1995); derivates of heptane arise during pulmonary tuberculosis (Phillips et al. 2007); and the use of VOCs as cancer biomarkers, especially for lung cancer, has been extensively studied in the literature (Chen et al. 2007; Bajtarevic et al. 2009; Matsumura et al. 2010). In terms of their exogenous production, various and numerous products in daily use may cause VOC exposure, such as cleaning products, paints, solvents, personal care products, automotive exhaust, or tobacco smoking. They may be absorbed as contaminants through the skin or taken up via inhalation or ingestion.

Although VOCs have been measured in various biological fluids, their characterization in human amniotic fluid (AF) has not been investigated to date. This physiological liquid contained in the amnion cavity constitutes a protective area around the conceptus, allowing its movement and harmonious growth. Aside from its physical protective effects (mechanical and thermal protection), AF also plays a biochemical defensive role and is an essential component of normal fetal development and morphogenic maturation. It is also a dynamically changing nutrient reservoir that includes fetal and maternal proteins, amino acids, carbohydrates, hormones, lipids, and electrolytes. This complex composition results from the diffusion of metabolites and water from maternal plasma, placenta, and developing fetal urinary, respiratory, and alimentary tracts.

Considering the potential negative effects of VOC exposure during the fetal period and the anatomical direct (cutaneous or inhalation) contact of the fetus with AF during pregnancy, this study aimed to detect these molecules in AF at the end of normal pregnancy and investigate their links to the lifestyle habits of women during pregnancy.

Materials and Methods

Subject Information

This study was based on a prospective cohort of 76 pregnant women with amniocentesis in the second trimester of pregnancy for cytogenetic-based diagnostics recruited at the Clermont-Ferrand Teaching Hospital between January and September 2019. The inclusion criteria were pregnant women aged 18 years or older, with an agreement for the use of their AF, during a healthy pregnancy leading to a healthy baby with a normal karyotype. Maternal data (age, weight, size, body mass index, gestational age, and ethnic group), mode of delivery (natural delivery or caesarean), and clinical information about the newborn (sex, size, weight, head circumference, and Apgar score at birth) were obtained from obstetrical and neonatal medical records and individual questionnaires filled out at the time of sample collection. Information about the smoking, alcohol consumption, family antecedents, or medicine taking of the pregnant women was collected from this questionnaire. The questionnaire also included questions about home characteristics and living conditions: rural or city housing, type of heating (gas, wood, electric, or fuel oil), and use of air fresheners or cosmetic care products, such as fragrances. The personal or professional use of solvents (e.g. paints, floor varnishes, and glues) was also noted. In order to estimate potential occupational exposure to VOCs, the profession the participants was also required. All the subjects signed an informed consent form, and the protocol was approved by the local ethics committee. The project was authorized by the Ethics Committee CPP Sud-Est VI, with CPP reference no. AU 765 and CODECOH no. DC-2008-558.

Sample Collection Protocol

Immediately after amniocentesis, 5 mL of amniotic liquid was transferred to a 10 mL glass vial sealed with butyl-Teflon septum caps and stored at − 80 °C before analysis (VWR International, France).

VOC Extraction and Analysis

The VOCs were extracted using a multi-purpose sampler (model MPS2, GERSTEL, Baltimore, MD, USA) through the following steps: pre-heating of the sample for 60 min at 70 °C using a stirrer (250 rpm), trapping of the volatile compounds of the headspace for 30 min at 20 °C using a solid phase microextraction fibre (75 µm carboxen-polydimethylsiloxane for Merlin Microseal, 23 gauge needle, auto holder, Supelco, Bellefonte, PA, USA), and thermal desorption of the trapped volatile compounds by introducing the fibre into a gas chromatograph (GC) injector. The splitless injection of volatile components into a GC (GC6890, Agilent) coupled to a mass spectrometer (MS5973, Agilent) was achieved through the thermal desorption of the fibre at 280 °C. The desorbed compounds were then separated through high-resolution gas-phase chromatography (capillary column SPB-5: 60 m length × 0.32 mm i.d. × 1 μm film thickness) (Supelco, Bellefonte, PA, USA). The oven temperature of the GC was maintained at 40 °C for 5 min and increased to 230 °C for 2 min, according to a gradient of 3 °C/min. Helium (99.9999% pure, Messer) was used as a carrier gas at a constant flow rate of 1 mL/min. The temperature of the GC–MS interface was 280 °C. The electron impact energy was set to 70 eV, and data were collected in the range of 20–250 atomic mass units (amu) in the first 10 min and in the range of 33–300 amu from 10 to 70 min. Identification was performed by comparing the experimental spectra with those of the Wiley275 mass spectral database (Hewlett-Packard Co., 1995) and by comparing the retention indices with those of the Bio-Sens internal database (VOCELIA®). For every VOC identified in the samples, abundance was calculated by measuring the peak area. The results were expressed as relative abundance (%) and were calculated by dividing the abundance of each compound by the abundance sum of all the compounds detected. Four external standards were used to correct the instrumental signal drifts: 1-bromo-butane (purity 99.7%), 1-bromo-decane (purity 98%), 1-bromo-heptane (purity 99.0%), and 1, 4-dibromobenzene (purity 98.0%) (Sigma-Aldrich Chimie, St-Quentin-Fallavier, France). The retention indices of these standards were distributed evenly over the sample GC chromatograms. The standards were analysed using the same analytical conditions as in the samples.

Statistics

Statistical analysis was performed using R software (http://www.R-project.org). The continuous data were presented according to a statistical distribution using the mean ± standard deviation. The assumption of normality was checked using normal probability plots and the Shapiro–Wilk test. To (i) analyse the relationships between the VOCs and the living conditions of the population, such as smoking, type of heating, usage of air fresheners and fragrance, and exposure to solvents, and to (ii) identify the groups of patients with similar VOCs, factorial analyses were performed rather than the more conventional statistical inferential approaches. The significance of the association was tested using the chi-square or Fisher’s exact test, which did not provide information on the significant individual associations between row–column pairs. Factorial analyses show how the variables are related, not just whether a relationship exists, and can handle a large amount of data to unfold hidden patterns. A two-step statistical plan analysis was proposed. In the first step, multiple correspondence analysis (MCA)—which is an extension of correspondence analysis or a generalization of principal component analysis (PCA) for categorical variables rather than quantitative variables—was applied to study the associations between VOCs and living conditions. MCA is an exploratory method that performs cross-tabulations, and it can be considered a useful tool for uncovering the relationships between categorical variables (Sourial et al. 2010). Whereas PCA is preferred for continuous parameters, MCA is applied to contingency tables, with the aim of transforming a table of numerical information into a graphical display in which each row and each column are illustrated as a point. All variables in a data set can be related to each other without differentiation between the explanatory and descriptive variables. The result is a representation of the two first discriminant plane projections of the discriminant scores of the patients and VOCs. Because the objective of the MCA was to determine profiles, it was impossible to consider VOCs that were not discriminating (always present or still absent) for this analysis. Thus, we used only VOCs present in 10–90% of the pregnant women. In the second step, hierarchical clustering (HC) was used to confirm groups of patients sufficiently close according to the relationships between the VOCs and living conditions as defined by MCA. HC does not require pre-specifying the number of clusters to be generated. To determine which clusters should be combined, a measure of dissimilarity between the sets of observations and a linkage criterion (Ward’s minimum variance method), which specifies the dissimilarity of sets as a function of the pairwise distances of observations in the sets, were defined. To apply this method, in the initial step, all clusters are singletons. Then, in each step, the pair of clusters that leads to a minimum increase in the total within-cluster variance after merging is determined. This increase is a weighted squared distance between the cluster centres. To apply a recursive algorithm under this objective function, the initial distance between the individual objects must be proportional to the squared Euclidean distance. The result is a tree-based representation of the observations called a dendrogram, which uses a pairwise distance matrix between patients as a clustering criterion.

Results

Description of the Population

The AF samples were collected from 76 pregnant women aged 20–43 years who underwent amniocentesis in the second trimester of pregnancy (gestational age 17.9 ± 1.6 weeks) for cytogenetic-based diagnostics. The maternal data are summarized in Table 1. Delivery was spontaneous in 88.2% of the women and occurred through natural birth in 77.6%. The rate of caesarean delivery was 22.4%, of which 41.2% were planned. Concerning the newborn sex ratio, 52.6% were female, and 47.4% were male. The average size of the newborns was 49.8 ± 2.1 cm. The Apgar scores were 8.7 ± 1.3, 9.5 ± 1.0, and 9.8 ± 0.5 at 1, 5, and 10 min after birth, respectively. As in previous parameters, the mean birth weight (3252 ± 503 g) and head circumference (34.6 ± 2.1 cm) were also in the usual range. The outcome was normal for all newborns included.

Table 1 Description of the experimental population of pregnant women (n = 76)
Full size table

Home Characteristics, Living Conditions, and Professional Situation

Overall, 51.7% of the pregnant women lived in rural areas and 48.3% in cities (Table 1). Gas was the most-used type of heating (46.1%) (Table 1). The majority of the women used cosmetic care products, such as fragrances, whereas few of them used air fresheners (Table 1). A total of 28% of subjects worked in the medical field, in hairdressing, in hotels, or did household or agricultural work and were considered to be occupationally exposed, whereas the others, without a profession or with an administrative job, were considered not professionally exposed (Table 1). The percentage of pregnant women potentially occupationally exposed (28%) was comparable with the percentage of pregnant women who auto-declared the use of solvents (personal or professional) (22.4%).

Volatile Organic Compounds

A total of 126 different VOCs were detected in human AF. Table 2 shows the chemical classification, frequency, relative abundance, and origins of the VOCs. The identified VOCs belonged to 13 chemical families. They were present in 2.6–100% of the AF samples, and their relative abundance was 0.002–63.300. With a higher relative abundance (63.300), acetone was quantitatively the most important VOC detected and was present in all 76 AF samples tested. Among the 126 VOCs detected, 29 others, aside from acetone, were present in all the AF samples, and 8 of them had a relative abundance higher than 1: benzaldehyde, p-cymene, diphenyl ether, propan-2-ol, propan-1-ol, 4-Methylpentan-1-ol, butan-2-one, and pentan-2one. Benzaldehyde is known to be implicated in the metabolic pathway of phenylalanine, and p-cymene is present in essential oils (cosmetic and alimentary products). Most of the VOCs identified (92/126) were from exogenous origins and belonged to chemical families, such as alkanes, Maillard compounds, benzenes, halogens, terpenes, and ethers. The endogenous or exogenous origin of these compounds was determined by performing bibliographic research in pubchem with the CAS number. According to the CMR codification (a European harmonized classification of carcinogenic (C), mutagenic (M), and toxicity for reproduction (R) substances), among the 126 VOCs detected, 3 of them were known to be carcinogenic (dichloromethane, trichloromethane, benzene), 1 (benzene) to be mutagenic, and 4 (styrene, toluene, carbon disulfide, trichloromethane) to be reprotoxic.

Table 2 Characteristics of the volatile organic compounds detected in amniotic fluid
Full size table

Statistical Links Between VOCs and Maternal Characteristics

Statistical analysis differentiated six clusters of patients characterized by specific VOC profiles and/or maternal characteristics in terms of living conditions (Fig. 1). Groups 1–6 were composed of 19, 11, 7, 12, 8, and 19 pregnant women, respectively. Each of the six VOC profiles was defined statistically by the presence of specific VOCs and the absence of others in the majority of patients from the cluster considered. Group 1 (Fig. 1a) was characterized by electric heating and a profile of 18 VOCs composed of MetCldiF, which was present in 100% of 19 pregnant women, and PaneN, 159cym, Oane, Bol3CH3, Oal, 2Hone4CH3, BoneCH3, Hone6CH3, ClBol, Fur25CH3, Fur3CH3, TetHfur, S2CH3, D3Car, Linalyl, Terpol, and 2PolMet, which were absent in the majority of the women in this cluster. BuTal and Ethol, which were also present in 100% of the women in this cluster, were not statistically identified as a characteristic of Group 1 because they were equally present in the majority of the women in the five other groups. Similarly, allyl, which was absent in 19 women in the group, was not specified for this cluster because it was also absent in almost all patients in the other 5 groups. The patients in Group 2 (Fig. 1b) were specified as non-solvent users, and their VOC profile was poor, as in Group 1. Group 2 was statistically characterized by the presence of Oal, x4ditert, and S2CH3 (in more than 75% of the women in this group) and by the almost total absence of nine compounds: tertBut, 2PoneDib, 2PolMet, Terpol, D3Car, Thii, Cymde, Bol3CH3, and 2Bol2CH3. The VOC profiles of Groups 1 and 2 can be clearly classified as poor because they were characterized by the absence of VOCs rather than by their presence. Group 3 (Fig. 1c) included seven patients who were characterized by smoking and a VOC profile constituting six compounds: AcCH3, which was absent in more than 75% of the women in this group, and PaneN, Benz, Sty, Fur25CH3, and Fur3CH3, which were present in all seven patients. Among these five compounds, four belonged to two chemical families (benzenes and Maillard compounds) and were all identified in the literature on tobacco or tobacco smoke. Groups 4 (Fig. 1d) and 5 (Fig. 1e) were characterized only by specific VOC profiles and not by lifestyle habits. Group 6 (Fig. 1f) was defined by the use of fragrance, smoking, and a rich VOC profile with 21 compounds (Oane, Tane, B2ol2CH3, Bol3CH3, Oal, 2Pone4CH3, Hone6CH3, Benzal, Fur24CH3, Fur3CH3, S02, D3Car, Euyptol, IsoMone, Linalool, Linalyl, Men3one, Terpol, AcCH3, AcPro2CH3, and Buteth) present in almost all 19 patients in this cluster, along with the absence of benzF. The 21 VOCs mostly had exogenous origins, with 11 identified in the literature on tobacco or tobacco smoke and 17 known to be present in fragrances. Most of the Group 6 specific compounds (7/22) were terpenes.

Fig. 1
figure 1figure 1figure 1

Volatile organic compound (VOC) profiles. Volatile organic compound (VOC) profiles and lifestyle habits of the six clusters of pregnant women. Statistical analyses were performed only on the VOCs (n = 58) present in 10–90% of the pregnant women. Six clusters (Groups 1 (a), 2 (b), 3 (c), 4 (d), 5 (e), 6 (f)) of patients were identified using specific VOC profiles and/or lifestyle habits. *VOC and lifestyle habit characteristics of the cluster considered. For these specific compounds, we determined whether they were known to be present in fragrance (P), tobacco, or smoke (C) and whether they had endogenous (En) or exogenous (Ex) origins. The figures are interpreted in relation to the others. The correspondence between the abbreviated and complete names of the chemical compounds is described in Table 2

Full size image

Discussion

Considering the potential negative effects of VOCs on fetal health, their significant emissions in atmospheric air due to pollution, and their presence in various and numerous products of daily use, VOC exposure during pregnancy is interesting to investigate to evaluate their effects on the fetus. Works studying the fetal exposure of VOC and the adverse outcome in health have adopted a traditional approach by predicting air pollution with mathematical models (Williams et al. 2019; Nakhjirgan et al. 2019) or with questionnaires (Nakaoka et al. 2021). Other studies have measured VOC concentrations in indoor/outdoor air (Ghosh et al. 2013; Helen et al. 2015; Chang et al. 2017, 2018; Caron-Beaudoin et al. 2022; Ghassabian et al. 2023), or measured the metabolites of these compounds in the body fluid (urine) (Boyle et al. 2016; Caron-Beaudoin et al. 2018; Weinstein et al. 2020; Ronde et al. 2022; Li et al. 2023) of pregnant women. With advances in analytical techniques, human biomonitoring involving measurement of biomarkers in body fluids, such as blood, urine, or exhaled air, is recognized as a more appropriate method for assessing health risk than environmental monitoring, since it evaluates the internal dose, achieving an estimate of the biologically active burden of the chemicals. The strength and the originality of our work lies in the fact that (1) it evaluated fetal exposure to VOCs by measuring the concentrations of these compounds not in the pregnant women’s fluids (blood or urine) but directly in a fetal fluid (AF) and (2) it did not focus on quantitative determination of specific VOCs but performed a broad screening of these compounds. A limitation of the study is that the screening method is semi-quantitative, so the level of VOCs obtained (Table 2) is expressed in relative abundance and cannot be compared with the majority of the results from other studies. Only one previous study examined these compounds in a fetal biological fluid—the blood cord—but on a limited panel of compounds (Dowty et al. 1976). The VOCs present in AF reflect maternal–foetal passage, and the fetus is bathed in AF; hence, it is in direct (cutaneous or inhalation) contact with these compounds, so measuring them in this fluid provides the best estimate of fetal exposure, whereas measurement of these compounds in maternal fluids or ambient air only provides an indirect and incomplete estimate of exposure.

In the literature, there are no data on the concentration of VOCs in the blood of pregnant women, since works which have used human biomonitoring to assess VOC exposure during pregnancy measured these chemical compounds only in urine, probably because of the ease with which it can be collected (no invasiveness of sampling and no need for the presence of professional operators). VOC metabolites in urine are considered reliable biomarkers for assessing exposure to VOCs owing to their specificity and their longer half-lives in the human body compared to the parent compounds (Alwis et al. 2012). After entering the body, VOCs are mainly metabolized by the hepatic cytochrome P450 pathway and excreted through urine (Alwis et al. 2012; Ghosh et al. 2013). Our study showed the presence of VOCs (parent compounds) in AF, which may indicate direct passage of these compounds through placental transfer and a lack of metabolism by the immature fetal liver.

To identify the sources of VOC exposure, we used a questionnaire—an indirect approach whose accuracy is dependent on the participants’ honesty. We established that many VOCs (n = 126) were present in the AF, with the majority resulting from environmental (exogenous) sources. We identified more VOCs (126) in the AF samples of pregnant women than in Dowty et al.’s study in 1976 (Dowty et al. 1976). In this previous work, only 12 VOCs were identified in blood cord. This difference is probably due to the better sensitivity of our analytical methodology and the smaller sample size of pregnant women recruited in this previous work (n = 11). However, this observation could suggest that exposure to environmental sources of VOCs is actually more frequent now than in the past. Home living conditions, smoking, use of fragrances, and non-use of solvents were associated with a specific VOC profile. Thus, the six groups of pregnant women were identified according to their living conditions and VOC profiles. Group 3 was particularly interesting because it was characterized by smoking and the presence of VOCs (4/5) that belong to the chemical families of benzene and Maillard compounds, known to be present in smoking or tobacco components. Among these VOCs, 2,5-dimethylfuran is a highly selective breath biomarker of active smoking and a robust marker of smoking contamination in indoor environments (Gordon et al. 2002; Alonso et al. 2010). We confirmed a direct association between smoking and the finding of tobacco metabolite constituents in AF, as previously described by Boyle et al. (2016) in pregnant women. However, in their study, VOCs were not measured in AF but in urine. Considering the carcinogenic and mutagenic properties of these compounds, their presence in AF supports the hypothesis of the negative effects of maternal (active or passive) smoking on newborns’ health. Smoking and fragrance use also characterized Group 6. Its VOC profile was consistent with these lifestyle habits. In included components identified in cigarettes and those that belong to the chemical family of terpene compounds known to be present in fragrances. Potential occupational exposure was not associated with a VOC profile. However, this result should be analysed with caution because occupational exposure was not assessed by measuring VOC levels in the professional environment of the participants but was estimated from their jobs.

Among the 126 VOCs identified, acetone had the highest relative abundance (63.3%) and was present in 100% of the AF samples. Under physiological conditions, acetone is produced by hepatocytes through the decarboxylation of acetoacetate, which is derived from lipolysis or lipid peroxidation. Ketone bodies in the blood, including acetoacetate and β-hydroxybutyrate, increase in all physiological situations (e.g. fasting, starving, or during a high-fat diet) in which the body uses fat instead of glucose for energy production (Laffel 1999). In terms of the origin of acetone in AF, it cannot be produced by the fetus because ketogenesis is not active but is of maternal origin. Maternal plasma ketone body levels increase as a consequence of physiologically enhanced adipose tissue lipolysis during pregnancy (free fatty acid oxidation and ketone body synthesis) (Bonvallot et al. 2013). The presence of acetone in AF is also explained by the fact that this compound can easily pass through the placenta (Herrera and Amusquivar 2000). Therefore, the fetus benefits from this product of maternal fatty acid metabolism. The activity of ketone body-metabolizing enzymes is present in fetal tissues (brain, liver, and kidney) and can be increased by conditions of maternal ketonemia, such as starvation during late pregnancy or high-fat feeding. These changes may represent an important adaptation to guarantee fetal brain development through the condition of limited availability of other substrates and a special preservation of this organ (Herrera 2002).

In this study, numerous (126) VOCS were identified in AF, and although some of them, such as dichloromethane, trichloromethane, benzene, styrene, toluene, and carbon disulfide, are well-known to be especially toxic, this was not correlated with adverse outcomes for newborns. This result is comparable to those of Nakhjirgan et al. (2019), who also observed no association between low body weight and VOC exposure, but is different from various studies that show a link between VOC exposure and adverse outcome at birth. These works are generally epidemiological retrospective studies which estimate VOC exposure by calculation. Hence, they are limited by their reliance on estimated exposure and thus are subject to bias due to potential exposure misclassification. In addition, these studies have often been performed in highly polluted areas, which may mean that the doses of pollutants involved were higher than those measured in this work, where pregnant women were recruited from the Auvergne, a French region with a medium level of industrialization and a low urban density. We may hypothesize that concentrations of VOCs were too low to induce toxic effects, and since this is a semi-quantitative study, comparison with safety criteria is not possible. The number of pregnant women is probably too low to observe an effect on birth outcome, contrary to epidemiological studies, which include a great number of participants. Finally, if prenatal exposure to toxicants is not associated with short-term adverse outcomes in this work, we cannot exclude the possibility that adverse long-term effects on the children’s health may develop. To study this point, it would be interesting to conduct a follow-up of the newborns during childhood with human fluid biomonitoring, as performed by Drago et al. (2020). In this birth cohort, named “Neonatal Environment and Health Outcomes” (NEHO), the authors have a project to measure VOCs in the placenta. Compared to this fetal matrix, the strength of AF is its simple composition (98% water plus electrolytes, proteins, peptides, carbohydrates, lipids, and hormones). Indeed, AF is classically studied to detect biomarkers, either of the normal development of the fetus or of the onset and evolution of disorders affecting the fetus’s or mother’s health (e.g. Down syndrome or intra-amniotic infection) (Smith and Blandford 1995).

Conclusion

Whereas the negative effects of VOCs on fetal or children’s health have been extensively studied by experimental or epidemiologic approaches, our study is the first to perform a broad screening of VOCs directly in a fetal fluid, AF, and to investigate their potential relationship with the lifestyle habits of women during normal pregnancy. This dynamic biological liquid is interesting to study because it allows for the monitoring of both the mother’s and the foetus’s health. In the AF samples collected from healthy pregnant women, 126 VOCs belonging to 13 chemical families were identified. The most abundant compound detected was the endogen metabolite acetone, which resulted from the mother’s fatty acid metabolism. Nevertheless, the majority of VOCs identified had exogenous origins (92/126) and were linked to lifestyle habits, especially smoking and fragrance use.

This study is the first to demonstrate the presence of and identify numerous VOCs in AF. Although some of them are known to be toxic, no adverse outcome for the newborns was observed, which may be explained by low VOC concentrations or small sample size. Future studies are now required to perform a quantitative determination of these components in order to compare levels with safety criteria and to evaluate the long-term issues of this early exposure to VOCs.