Use of meconium in perinatal epidemiology: potential benefits and pitfalls

Meconium as an Analyte for Androgen Exposure: Analysis Through Varying Maternal-Fetal Biomarkers

Meconium, the first stool produced by neonates, has been used as an analyte for exogenous fetal exposures. However, few studies have investigated the relationship between meconium and androgen exposure in utero. Here, we examine the associations of testosterone and dehydroepiandrosterone (DHEA) across maternal antenatal salivary testosterone, cord blood, meconium, and infant salivary testosterone. A total of 47 women with singleton, uncomplicated pregnancies, and their infants were included in this study. Participants were recruited from an academic obstetric clinic. Maternal saliva was collected at 36-weeks' gestation. Cord blood and meconium were collected at birth. Infant salivary testosterone was collected at 1 and 4 weeks of age. Multivariate model results showed that meconium testosterone was associated with neonatal testosterone at 1 (F = 5.62, p = 0.029) and 4 weeks (F = 4.28, p = 0.048) postnatal age; no sex differences were detected. This study suggests meconium is a valuable tool for evaluating endogenous androgen exposure and should be used in future studies to investigate the fetal hormonal milieu.

First Insight into Fetal Exposure to Legacy and Emerging Plasticizers Revealed by Infant Hair and Meconium: Occurrence, Biotransformation, and Accumulation

Epidemiological studies have demonstrated the embryonic and developmental toxicity of plasticizers. Thus, understanding the in utero biotransformation and accumulation of plasticizers is essential to assessing their fate and potential toxicity in early life. In the present study, 311 infant hair samples and 271 paired meconium samples were collected at birth in Guangzhou, China, to characterize fetal exposure to legacy and emerging plasticizers and their metabolites. Results showed that most of the target plasticizers were detected in infant hair, with medians of 9.30, 27.6, and 0.145 ng/g for phthalate esters (PAEs), organic phosphate ester (OPEs), and alternative plasticizers (APs), and 1.44, 0.313, and 0.066 ng/g for the metabolites of PAEs, OPEs, and APs, respectively. Positive correlations between plasticizers and their corresponding primary metabolites, as well as correlations among the oxidative metabolites of bis(2-ethylhexyl) phthalate (DEHP) and 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), were observed, indicating that infant hair retained the major phase-I metabolism of the target plasticizers. While no positive correlations were found in parent compounds or their primary metabolites between paired infant hair and meconium, significant positive correlations were observed among secondary oxidative metabolites of DEHP and DINCH in hair and meconium, suggesting that the primary metabolites in meconium come from hydrolysis of plasticizers in the fetus but most of the oxidative metabolites come from maternal-fetal transmission. The parent compound/metabolite ratios in infant hair showed a decreasing trend across pregnancy, suggesting in utero accumulation and deposition of plasticizers. To the best of our knowledge, this study is the first to report in utero exposure to both parent compounds and metabolites of plasticizers by using paired infant hair and meconium as noninvasive biomonitoring matrices and provides novel insights into the fetal biotransformation and accumulation of plasticizers across pregnancy.

In Utero Exposure to Caffeine and Acetaminophen, the Gut Microbiome, and Neurodevelopmental Outcomes: A Prospective Birth Cohort Study

Pregnant individuals are exposed to acetaminophen and caffeine, but it is unknown how these exposures interact with the developing gut microbiome. We aimed to determine whether acetaminophen and/or caffeine relate to the childhood gut microbiome and whether features of the gut microbiome alter the relationship between acetaminophen/caffeine and neurodevelopment. Forty-nine and 85 participants provided meconium and stool samples at 6-7, respectively, for exposure and microbiome assessment. Fecal acetaminophen and caffeine concentrations were quantified, and fecal DNA underwent metagenomic sequencing. Caregivers and study staff assessed the participants' motor and cognitive development using standardized scales. Prenatal exposures had stronger associations with the childhood microbiome than concurrent exposures. Prenatal acetaminophen exposure was associated with a trend of lower gut bacterial diversity in childhood [β = -0.17 Shannon Index, 95% CI: (-0.31, -0.04)] and was marginally associated with differences in the relative abundances of features of the gut microbiome at the phylum (Firmicutes, Actinobacteria) and gene pathway levels. Among the participants with a higher relative abundance of Proteobacteria, prenatal exposure to acetaminophen and caffeine was associated with lower scores on WISC-IV subscales. Acetaminophen during bacterial colonization of the naïve gut is associated with lasting alterations in childhood microbiome composition. Future studies may inform our understanding of downstream health effects.

Meconium androgens are correlated with ASD-related phenotypic traits in early childhood in a familial enriched risk cohort

BACKGROUND

Prenatal exposure to increased androgens has been suggested as a risk factor for autism spectrum disorder (ASD). This hypothesis has been examined by measurement of steroids in amniotic fluid, cord blood, saliva, and blood with mixed results.

METHODS

To provide an orthogonal measure of fetal exposure, this study used meconium, the first stool of a newborn, to measure prenatal androgen exposure from infants in the Early Autism Risk Longitudinal Investigation (EARLI). EARLI is a familial-enriched risk cohort that enrolled pregnant mothers who already had a child with an ASD diagnosis. In the younger child, we investigated the association between meconium unconjugated (u) and total (t) concentrations of major androgens testosterone (T), dehydroepiandrosterone (DHEA), and androstenedione (A4), and ASD-related traits at 12 and 36 months of age. Traits were measured at 12 months with Autism Observation Scale for Infants (AOSI) and at 36 months with total score on the Social Responsiveness Scale (SRS). One hundred and seventy children had meconium and AOSI, 140 had meconium and SRS, and 137 had meconium and both AOSI and SRS.

RESULTS

Separate robust linear regressions between each of the log-transformed androgens and log-transformed SRS scores revealed three-way interaction between sex of the child, sex of the proband, and testosterone concentration. In the adjusted analyses, t-T, u-A4, and u-DHEA (P ≤ 0.01) were positively associated with AOSI scores, while u-T (P = 0.004) and u-DHEA (P = 0.007) were positively associated with SRS total score among females with female probands (n = 10). Additionally, higher concentrations of u-T (P = 0.01) and t-T (P = 0.01) predicted higher SRS total score in males with male probands (n = 63). Limitations Since we explored three-way interactions, this resulted in a limited sample size for some analyses. This study was from an enriched-risk cohort which may limit generalizability, and this study used ASD-assessment scales as outcomes instead of diagnostic categories. Additionally, the novel use of meconium in this study limits the ability to compare the results in this cohort to others due to the paucity of research on meconium.

CONCLUSIONS

This study supports the utility of meconium for studies of endogenous fetal metabolism and suggests the sex of older siblings with autism should be considered as a biological variable in relevant studies.

Comparison of protease and aminopeptidase activities in meconium: A pilot study

The successive accumulation of proteases and aminopeptidases in meconium are important physiological components of the intrauterine environment in which a fetus develops. The aim of the present study was to assess the changes in the activities of these enzymes in meconium of healthy infants, and to investigate whether there were any statistically significant associations between activity of the enzymes of interest and the mode of delivery. The activities of proteases and aminopeptidases were determined in meconium portions (n=110) using the substrates BODIPY FL casein and L-leucine-7-amido-4-methylcoumarin hydrochloride, respectively. Serial meconium samples (2-5 per neonate) were collected from healthy infants born vaginally (n=14), and by a cesarean section (n=16). Protease activity (10⁴ RFU/h) was lower in the first meconium sample compared with the final sample from the same infant (3.99±2.03 vs. 5.76±2.24, respectively, mean ± standard deviation; P=0.004). Conversely, there was no significant difference in aminopeptidase activity (10³ nM/l/h) between consecutive meconium samples (P=0.702). The ratios of the first-meconium sample enzyme activity to the last-meconium sample enzyme activity were lower for proteases compared with aminopeptidases (0.76±0.48 vs. 1.35±1.04, respectively mean ± standard deviation; P=0.014), and sustained in the infants born by a cesarean section (P=0.008). Spearman's correlation coefficient analysis between the first and last meconium samples showed the correlation increased in the infants born vaginally compared with the rest of the infants (proteases, R=0.618 vs. R=0.314; aminopeptidases, R=0.688 vs. R=0.566). Aminopeptidase activity did not exhibit any notable dynamic changes during meconium accumulation in the fetal intestine. In infants born vaginally compared with those born by a cesarean section, the activity of both proteases and aminopeptidases in the first meconium sample showed an improved correlation with the activity of the final meconium sample. This may suggest that in the intrauterine environment, during accumulation of meconium in the digestive tract of the fetus, the activity and/or levels of these enzymes and the substrates they catalyze were more stable in newborns born vaginally compared with infants born by caesarean section.

Mercury speciation in meconium and associated factors

Meconium is formed early in gestation and it is normally not excreted until after birth. Thus it may provide a longer and cumulative record of exposure to mercury (Hg). The present study aims to speciate Hg in meconium samples (N = 488) from Slovenian and Croatian new-borns prenatally exposed to low levels of methyl-Hg (MeHg) from maternal seafood intake and to Hg⁰ from maternal dental amalgam fillings. We had complete data of total Hg (THg) and MeHg in meconium and THg in maternal hair (MH), while THg and MeHg in maternal blood (MB) were available only for Croatian mothers. Personal data namely maternal seafood intake, age, pre-pregnancy BMI, parity, smoking, estimated gestational age at birth, sex, and birth weight were available for the majority of participants, except the number of dental amalgams which was in most cases missing for Croatian mothers. The median THg concentration in meconium was 11.1 (range: 0.41-375.2) ng/g and inorganic Hg (Hg(II)) presented 98.8% (range: 82%-100%, CV: 2%) of THg. We observed significant correlation between meconium and MH Hg levels, with the highest correlation between hair THg and meconium MeHg. Correlation analysis including MB (available only for Croatian population) showed a significant positive correlation between THg in meconium and THg in MB (R_s = 0.642). Additionally, MeHg from MB was correlated with MeHg in meconium (R_s = 0.898), while the correlation between Hg(II) in MB and meconium was positive, but not significant. Maternal seafood intake was significantly correlated with meconium MeHg (R_s = 0.498) and Hg(II) (R_s = 0.201). Multiple linear regression (performed on the Slovenian population, N = 143) confirmed a positive association between meconium MeHg and seafood intake. Furthermore, meconium Hg(II) was positively associated with the number of maternal dental amalgam fillings, but linear regression models did not confirm correlation between seafood intake and meconium Hg(II) levels. We assume that Hg⁰ released from maternal dental amalgam fillings and MeHg from seafood intake were both transported through the placental barrier and portioned between different foetal compartments including meconium. Weak correlation between maternal seafood intake and Hg(II) levels in meconium suggests that there is certain evidence of MeHg demethylation. However, because this correlation was not confirmed by the multiple regression, MeHg demethylation during prenatal life cannot be neither confirmed nor excluded. Further investigations at higher level of exposure are needed to confirm this observations. We can conclude that meconium is a suitable biomarker for MeHg and Hg⁰ exposure during pregnancy. However, comparability of the results reported in meconium in different studies is hindered by a lack of standardized sampling protocols, storage, and analysis.

Preliminary results of identification and quantification of paclitaxel and its metabolites in human meconium from newborns with gestational chemotherapeutic exposure

Objective

Cancer diagnosis during pregnancy occurs in 1 out of 1000 pregnancies with common malignancies including breast and hematological cancers. Fetal exposure to currently utilized agents is poorly described. We directly assessed fetal exposure by screening meconium from 23 newborns whose mothers had undergone treatment for cancer during pregnancy.

Study design

Meconium was collected from newborns whose mothers were diagnosed with cancer during pregnancy and underwent chemotherapy in the second or third trimester as part of the Cancer and Pregnancy Registry. We conducted screening of 23 meconium samples for chemotherapeutics and known metabolites of chemotherapeutics by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Putative identification of paclitaxel and/or its metabolites was made in 8 screened samples. In positively screened samples, we quantified paclitaxel, 3’-p-hydroxypaclitaxel, and 6α-hydroxypaclitaxel by stable isotope dilution-LC-HRMS.

Results

Mean (standard deviation) levels of paclitaxel in positively screened samples were 399.9 (248.6) pg/mg in meconium samples from newborn born to mothers that underwent chemotherapy during pregnancy. 3’-p-hydroxypaclitaxel and 6α-hydroxypaclitaxel mean levels were 105.2 (54.6) and 113.4 (48.9) pg/mg meconium, respectively.

Conclusion

Intact paclitaxel, 3’-p-hydroxypaclitaxel, and 6α-hydroxypaclitaxel were detected in meconium, providing unambiguous confirmation of human fetal exposure. Variability in meconium levels between individuals may indicate a potential for reducing fetal exposure based on timing, dosing, and individual characteristics. This preliminary study may provide an approach for examining the effects of cancer diagnosis during pregnancy on other outcomes by providing a measure of direct fetal exposure.

Differences in testosterone and its precursors by sex of the offspring in meconium

Prenatal metabolism exerts profound effects on development. The first stool of the newborn, meconium, provides a window into the prenatal metabolic environment. The objective of this study was to examine the feasibility of meconium as a novel matrix to quantify prenatal steroid levels. We quantified parameters of analytical interest regarding the use of meconium, including sample stability. We hypothesized that meconium steroid content would differ by sex, prompting analysis of meconium to test effects of prenatal steroid metabolism. Meconium from 193 newborns enrolled in the Early Autism Risk Longitudinal Investigation (EARLI) study, including 107 males, and 86 females, were analyzed by isotope dilution-liquid chromatography-high resolution mass spectrometry (ID-LC-HRMS) while blinded to identity for testosterone (T), androstenedione (AD), and dehydroepiandrosterone (DHEA). Steroid levels were compared by sex, and investigations of potential trends resulting from sample storage or processing was conducted. The unconjugated steroid content of meconium in ng/g (mean, standard deviation) was for males: T (2.67, 8.99), AD (20.01, 28.12), DHEA (13.96, 23.57) and for females: T (0.82, 1.63), AD (22.32, 24.38), DHEA (21.06, 43.49). T was higher in meconium from males (p=0.0333), and DHEA was higher in meconium from females (p=0.0202). 6 female and 3 male T values were below the limit of detection. No extreme variability in hydration or trend in steroid levels by storage time was detected. Sexually dimorphic levels of hormones may reflect gestational differentiation, and future studies should consider meconium analysis.

Second trimester amniotic fluid bisphenol A concentration is associated with decreased birth weight in term infants

Bisphenol A (BPA) is an endocrine disrupting chemical with ubiquitous environmental exposure. Animal studies have demonstrated that in utero BPA exposure leads to increased adult body weight. Our aim was to characterize human fetal BPA exposure by measuring BPA concentration in second trimester amniotic fluid (AF) samples and to study its relationship with birth weight (BW) in full term infants. To achieve these goals, we developed a total BPA assay utilizing derivatization with pentafluorobenzyl followed by analysis with LC-ECAPCI-MS/MS with a limit of detection of 0.08ng/mL and limit of quantification (LOQ) of 0.25ng/mL. The mean BW of infants with AF BPA 0.40-2.0ng/mL was 241.8g less than infants with AF BPA less than the LOQ after controlling for covariates (p=0.049). No effect was seen outside this range indicating a non-monotonic effect. Our data suggest that low level BPA exposure in utero decreases BW and needs further study.