Boston Birth Cohort profile: rationale and study design

Gestational DNA methylation age as a marker for fetal development and birth outcomes: findings from the Boston Birth Cohort

BACKGROUND

Gestational DNA methylation age (GAmAge) has been developed and validated in European ancestry samples. Its applicability to other ethnicities and associations with fetal stress and newborn phenotypes such as inflammation markers are still to be determined. This study aims to examine the applicability of GAmAge developed from cord blood samples of European decedents to a racially diverse birth cohort, and associations with newborn phenotypes.

METHODS

GAmAge based on 176 CpGs (Haftorn GAmAge) was calculated for 940 children from a US predominantly urban, low-income, multiethnic birth cohort. Cord blood DNA methylation was profiled by Illumina EPIC array. Newborn phenotypes included anthropometric measurements and, for a subset of newborns (N = 194), twenty-seven cord blood inflammatory markers (sandwich immunoassays).

RESULTS

GAmAge had a stronger correlation with GEAA in boys (r = 0.89, 95% confidence interval (CI) [0.87,0.91]) compared with girls (r = 0.83, 95% CI [0.80,0.86]), and was stronger among extremely preterm to very preterm babies (r = 0.91, 95% CI [0.81,0.96]), compared with moderate (r = 0.48, 95% CI [0.34,0.60]) and term babies (r = 0.58, 95% CI [0.53,0.63]). Among White newborns (N = 51), the correlation between GAmAge vs. GEAA was slightly stronger (r = 0.89, 95% CI [0.82,0.94]) compared with Black/African American newborns (N = 668; r = 0.87, 95% CI [0.85,0.89]) or Hispanic (N = 221; r = 0.79, 95% CI [0.74,0.84]). Adjusting for GEAA and sex, GAmAge was associated with anthropometric measurements, cord blood brain-derived neurotrophic factor (BDNF), and monocyte chemoattractant protein-1 (MCP-1) (p < 0.05 for all).

CONCLUSIONS

GAmAge estimation is robust across different populations and racial/ethnic subgroups. GAmAge may be utilized as a proxy for GEAA and for assessing fetus development, indicated by inflammatory state and birth outcomes.

Association of pregnancy complications and postpartum maternal leukocyte telomeres in two diverse cohorts: a nested case-control study

BACKGROUND

Biologic strain such as oxidative stress has been associated with short leukocyte telomere length (LTL), as well as with preeclampsia and spontaneous preterm birth, yet little is known about their relationships with each other. We investigated associations of postpartum maternal LTL with preeclampsia and spontaneous preterm birth.

METHODS

This pilot nested case control study included independent cohorts of pregnant people with singleton gestations from two academic institutions: Cohort 1 (hereafter referred to as Suburban) were enrolled prior to 20 weeks' gestation between 2012 and 2018; and Cohort 2 (hereafter referred to as Urban) were enrolled at delivery between 2000 and 2012. Spontaneous preterm birth or preeclampsia were the selected pregnancy complications and served as cases. Cases were compared with controls from each study cohort of uncomplicated term births. Blood was collected between postpartum day 1 and up to 6 months postpartum and samples were frozen, then simultaneously thawed for analysis. Postpartum LTL was the primary outcome, measured using quantitative polymerase chain reaction (PCR) and compared using linear multivariable regression models adjusting for maternal age. Secondary analyses were done stratified by mode of delivery and self-reported level of stress during pregnancy.

RESULTS

156 people were included; 66 from the Suburban Cohort and 90 from the Urban Cohort. The Suburban Cohort was predominantly White, Hispanic, higher income and the Urban Cohort was predominantly Black, Haitian, and lower income. We found a trend towards shorter LTLs among people with preeclampsia in the Urban Cohort (6517 versus 6913 bp, p = 0.07), but not in the Suburban Cohort. There were no significant differences in LTLs among people with spontaneous preterm birth compared to term controls in the Suburban Cohort (6044 versus 6144 bp, p = 0.64) or in the Urban Cohort (6717 versus 6913, p = 0.37). No differences were noted by mode of delivery. When stratifying by stress levels in the Urban Cohort, preeclampsia was associated with shorter postpartum LTLs in people with moderate stress levels (p = 0.02).

CONCLUSION

Our exploratory results compare postpartum maternal LTLs between cases with preeclampsia or spontaneous preterm birth and controls in two distinct cohorts. These pilot data contribute to emerging literature on LTLs in pregnancy.

Distribution and correlates of plasma folate, vitamin B12, and homocysteine in a sample of low-income minority children aged 6 months to 9 years in the U.S

Background

Precision nutrition emphasizes tailoring dietary requirements across populations and life stages. Optimal folate and vitamin B12 levels are important for normal growth and development, but data are lacking for low-income minority U.S. children during early life periods. This study aimed to describe folate, vitamin B12, homocysteine (Hcy) levels, and influencing factors to address the gaps.

Methods

Blood samples from children aged 6 months to 9 years and mothers 48-72 hours postpartum in the Boston Birth Cohort (BBC) were tested for folate, vitamin B12, and Hcy. Maternal and child characteristics, sociodemographic factors, and feeding status were obtained from a standard maternal questionnaire interview at the enrollment and follow-up, and medical records. The distribution of children's folate, vitamin B12, and Hcy were described and factors influencing these biomarkers were analyzed.

Results

A wide distribution of folate, vitamin B12, and Hcy levels was observed in this sample, with longitudinal trends consistent with National Health and Nutrition Examination Survey (NHANES) data. Multivariate analysis showed that very preterm birth correlated with higher folate levels (adjusted β 4.236; 95% CI: 1.218, 7.253; p=0.006). Children aged 1-2 years and 3-8 years had lower folate levels compared to those <1 year (adjusted β -10.191 and -7.499 respectively; p<0.001). Vitamin B12 levels were higher in Black children (adjusted fold change 1.139; 95% CI: 1.052, 1.233; p=0.001) and those children whose mothers' B12 levels were at the highest quartile (Q4) (adjusted fold change 1.229; 95% CI: 1.094, 1.380; p=0.001). Delayed solid food introduction (> 6 months) correlated with lower children's B12 levels (adjusted fold change 0.888; 95% CI: 0.809, 0.975; p=0.013). Hcy levels were lower in Black children (adjusted fold change 0.962; 95% CI: 0.932, 0.993; p=0.018), higher in children with maternal Hcy levels in Q4 (adjusted fold change 1.081; 95% CI: 1.03, 1.135; p=0.002) and in children aged 3-8 years (adjusted fold change 1.084; 95% CI: 1.040, 1.131; p< 0.001).

Conclusions

This study revealed wide variations in plasma folate, vitamin B12, and Hcy levels among low-income minority U.S. children and identified race, maternal levels, child's age, prematurity, and timing of solid food introduction as significant correlates.

Early Life Origins of Neurodevelopmental Disabilities in the Boston Birth Cohort: Research findings and future directions

Neurodevelopmental disabilities (NDD) are a group of conditions with onset in early development period and is characterized by limitations in several functional domains. Autism spectrum disorder (ASD) and Attention-Deficit Hyperactivity Disorders (ADHD), the most common NDDs, have complex etiologies and possibly multiple pathways leading up to the manifestation of these disorders. Boston Birth Cohort (BBC) is a preterm enriched birth cohort, and over the years, researchers have used the BBC dataset to study a broad spectrum of early life protective and risk factors in the context of NDDs. Broadly, some of them include: 1) nutrition (e.g. maternal folate, vitamin B12, cord folate species, selenium), 2) metabolic factors (e.g. role of maternal diabetes, obesity, branched chain amino acids and other essential amino acids), 3) lipid metabolism (e.g. maternal cholesterol), 4) immune activation and/or systematic inflammation (including maternal immune activation, inflammation of the placenta, inflammatory markers, maternal antibiotic use and acetaminophen use), and 5) other factors associated with NDDs (e.g. maternal stress, sickle cell disease). The findings from these studies are discussed in this review. BBC studies have advanced the field of NDD in the following important ways: 1) generating evidence that sheds light on new exposures, 2) furthering the existing knowledge using better methodological approaches, 3) analyzing novel mechanistic pathways on already proven relationship, and 4) advancing knowledge on the under-studied minority population in the U.S. BBC researchers are involved in ongoing efforts to characterize NDD developmental trajectories across the life stages by integrating multi-omics data (genome, epigenome, and metabolome) to gain a deeper understanding of the molecular pathways by which early life factors drive or shape the developmental trajectories of NDDs.

Joint Associations of Pregnancy Complications and Postpartum Maternal Renal Biomarkers With Severe Cardiovascular Morbidities: A US Racially and Ethnically Diverse Prospective Birth Cohort Study

Background Pregnancy complications are risk factors for cardiovascular disease (CVD). Little is known about the role of renal biomarkers measured shortly after delivery, individually or in combination with pregnancy complications, in predicting subsequent severe maternal CVD. Methods and Results This study included 566 mothers of diverse races and ethnicities from the Boston Birth cohort, enrolled at delivery and followed prospectively. Plasma creatinine and CysC (cystatin C) were measured 1 to 3 days after delivery. CVD during follow-up was defined by physician diagnoses in electronic medical records. Associations of renal biomarkers and pregnancy complications with time-to-CVD events were assessed using Cox proportional hazards models. During an average of 10.3±3.2 years of follow-up, 30 mothers developed 1 or more CVDs. Only a modest association was observed between creatinine and risk of CVD. In comparison, we found that per 0.1 mg/L increase of CysC was associated with a hazard ratio (HR) of 1.2 (95% CI, 1.1-1.4) for CVD after adjusting for covariates. Compared with those without preeclampsia and with normal CysC level (≤75th percentile), mothers with preeclampsia and elevated CysC (>75th percentile) had the highest risk of CVD (HR, 4.6 [95% CI, 1.7-17.7]), whereas mothers with preeclampsia only or with elevated CysC only did not have significantly increased CVD risk. Similar synergistic effects for CVD were observed between CysC and preterm delivery. Conclusions In this sample of US, traditionally underrepresented multiracial and multiethnic high-risk mothers, elevated maternal plasma CysC, independently and jointly with pregnancy complications, increased risk of CVD later in life. These findings warrant further investigation. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT03228875.

Prospective Cohort Study of Emergency Department Visit Frequency and Diagnoses Before and During COVID-19 Pandemic in Urban, Low-Income, US- and Foreign-Born Mothers in Boston, MA

Background

The coronavirus 2019 (COVID-19) pandemic fundamentally changed how populations interface with the healthcare system. Despite historical spikes in US mortality during the pandemic, emergency department (ED) visits were paradoxically low. This is a concerning phenomenon that raises a red flag regarding access to care, especially among vulnerable populations. In this study we sought to understand how ED utilization evolved during the COVID-19 pandemic among traditionally understudied, low-income, racially diverse US- and foreign-born mothers.

Methods

This is a secondary analysis of a pre-existing dataset of 3,073 participants enrolled in the Boston Birth Cohort at birth and followed prospectively. We obtained ED visit diagnoses from 2019 and 2020 via electronic health records, categorized according to the International Classification of Diseases, 10th Revision, and compared them using graph plots, chi-square, and negative binomial regression.

Results

The number of ED visits decreased by 29.1% (P < 0.001) from 2019 (1,376) to 2020 (976). However, visits for infectious and parasitic diseases, including COVID-19, increased by 90.6% (32:61) with COVID-19 accounting for 77% of those visits in 2020 (47/61). Mental health-related visits increased by 40.9% (44:62), with diagnoses of alcohol use disorder increasing by 183% (6:17). Regression analysis showed 50% less ED utilization among foreign- vs US-born participants; however, the increase in infectious diseases visits was greater among foreign-born compared to US-born mothers (185% vs 26%, P = 0.01), while the increase in mental health diagnoses was greater among US-born mothers (69% vs -33%, P = 0.10).

Conclusion

Despite a decrease in total ED visits during the pandemic, there was an increase in COVID-19- (immigrant > US born) and mental health- (US-born only) related visits. Our findings demonstrate that EDs remain a critical access point for care for minority populations and have implications for preparedness, resources, and services of EDs in urban settings to better address the needs of communities. However, alternative avenues for healthcare services for these populations, particularly during health crises, warrant further investigation.

Association between acetaminophen metabolites and CYP2E1 DNA methylation level in neonate cord blood in the Boston Birth Cohort

BACKGROUND

Acetaminophen is a commonly used medication by pregnant women and is known to cross the placenta. However, little is known about the biological mechanisms that regulate acetaminophen in the developing offspring. Cytochrome 2E1 (CYP2E1) is the primary enzyme responsible for the conversion of acetaminophen to its toxic metabolite. Ex vivo studies have shown that the CYP2E1 gene expression in human fetal liver and placenta is largely controlled by DNA methylation (DNAm) at CpG sites located in the gene body of CYP2E1 at the 5' end. To date, no population studies have examined the association between acetaminophen metabolite and fetal DNAm of CYP2E1 at birth.

METHODS

We utilized data from the Boston Birth Cohort (BBC) which represents an urban, low-income, racially and ethnically diverse population in Boston, Massachusetts. Acetaminophen metabolites were measured in the cord plasma of newborns enrolled in BBC between 2003 and 2013 using liquid chromatography-tandem mass spectrometry. DNAm at 28 CpG sites of CYP2E1 was measured by Illumina Infinium MethylationEPIC BeadChip. We used linear regression to identify differentially methylated CpG sites and the "DiffVar" method to identify differences in methylation variation associated with the detection of acetaminophen, adjusting for cell heterogeneity and batch effects. The false discovery rate (FDR) was calculated to account for multiple comparisons.

RESULTS

Among the 570 newborns included in this study, 96 (17%) had detectable acetaminophen in cord plasma. We identified 7 differentially methylated CpGs (FDR < 0.05) associated with the detection of acetaminophen and additional 4 CpGs showing a difference in the variation of methylation (FDR < 0.05). These CpGs were all located in the gene body of CYP2E1 at the 5' end and had a 3-6% lower average methylation level among participants with detectable acetaminophen compared to participants without. The CpG sites we identified overlap with previously identified DNase hypersensitivity and open chromatin regions in the ENCODE project, suggesting potential regulatory functions.

CONCLUSIONS

In a US birth cohort, we found detection of cord biomarkers of acetaminophen was associated with DNAm level of CYP2E1 in cord blood. Our findings suggest that DNA methylation of CYP2E1 may be an important regulator of acetaminophen levels in newborns.

Longitudinal Trajectory and Early Life Determinant of Childhood Adipokines: Findings From a Racially Diverse Birth Cohort

CONTEXT

Leptin and adiponectin play important roles in systemic metabolic homeostasis, beginning in utero. Limited data exist on the levels and trajectories of these 2 hormones at birth and in childhood and their biological and social determinants.

OBJECTIVE

We examined the longitudinal trajectories of leptin and adiponectin from birth to early childhood, along with influential prenatal and infancy factors, and whether the trajectories and risk factors differ by preterm birth status.

METHODS

We included mother-infant pairs in the Boston Birth Cohort, a predominantly Black, indigenous, and people of color (BIPOC) study population. We measured infant plasma leptin and adiponectin levels at birth and in early childhood. We examined longitudinal trajectories and the associated prenatal maternal and infancy factors. We analyzed 716 infants (158 preterm) who had leptin and adiponectin measured at birth and in early childhood (mean corrected age 2.18 years [interquartile range, 0.4-10.4]).

RESULTS

Cord leptin was higher in term infants (40 230 vs 20 481 in preterm, P < 0.0001) but childhood leptin did not differ by prematurity (4123 in term vs 4181 in preterm, P = 0.92). Adiponectin was higher in term infants at birth (18 416 vs 11 223, P < 0.0001) and in childhood (12 108 vs 10532, P = 0.04). In stepwise regression, Black race was associated with higher childhood leptin and lower childhood adiponectin. Female sex was associated with higher childhood leptin levels and lower childhood adiponectin levels in multivariable regression models.

CONCLUSION

Our results highlight preterm status, race, and biological sex as predictors of adipokine trajectory throughout childhood. These findings raise the possibility that early life programming of adipokines may contribute to higher metabolic risk in life, especially among Black children born preterm.

Cord Blood Insulin Concentration and Hypertension Among Children and Adolescents Enrolled in a US Racially Diverse Birth Cohort

BACKGROUND

Although insulin resistance is closely related to hypertension, the debate continues as to whether insulin resistance is a cause or a consequence of hypertension. This study investigated the associations of cord blood insulin concentration with blood pressure (BP) and hypertension in childhood and adolescence.

METHODS

This study included 951 children enrolled from 1998 to 2012 and followed from birth onwards at the Boston Medical Center, Boston, MA. Cord blood insulin concentration was measured using a sandwich immunoassay. Hypertension in childhood and adolescence was defined based on the 2017 American Academy of Pediatrics Clinical Practice Guidelines.

RESULTS

The median (interquartile range) for cord blood insulin concentration was 12.1 (7.2-19.0) µIU/mL. The age range of BP measurements was 3 to 18 years (median, 10.6 years). Cord blood insulin concentration was positively associated with systolic and diastolic BP as well as the risk of hypertension at age 3 to 18 years. Compared with the lowest tertile of cord blood insulin concentration, the top tertile insulin concentration was associated with a 5.18 (95% CI, 1.97-8.39) percentile increase in systolic BP, 4.29 (95% CI, 1.74-6.84) percentile increase in diastolic BP, and 1.62-fold (95% CI, 1.27-2.08) higher risk of hypertension. The association between insulin and hypertension was stronger among children born preterm (P for interaction=0.048). Furthermore, preterm birth and childhood overweight or obesity enhanced the associations.

CONCLUSIONS

Our results suggest that elevated insulin concentration at birth plays a critical role in the early life origins of hypertension and support the hypothesis implicating insulin resistance in the etiology of hypertension.

Association of mitochondrial DNA content, heteroplasmies and inter-generational transmission with autism

Mitochondria are essential for brain development. While previous studies linked dysfunctional mitochondria with autism spectrum disorder (ASD), the role of the mitochondrial genome (mtDNA) in ASD risk is largely unexplored. This study investigates the association of mtDNA heteroplasmies (co-existence of mutated and unmutated mtDNA) and content with ASD, as well as its inter-generational transmission and sex differences among two independent samples: a family-based study (n = 1,938 families with parents, probands and sibling controls) and a prospective birth cohort (n = 997 mother-child pairs). In both samples, predicted pathogenic (PP) heteroplasmies in children are associated with ASD risk (Meta-OR = 1.56, P = 0.00068). Inter-generational transmission of mtDNA reveals attenuated effects of purifying selection on maternal heteroplasmies in children with ASD relative to controls, particularly among males. Among children with ASD and PP heteroplasmies, increased mtDNA content shows benefits for cognition, communication, and behaviors (P ≤ 0.02). These results underscore the value of exploring maternal and newborn mtDNA in ASD.

Most genetic studies of autism spectrum disorder (ASD) have focused on the nuclear genome. Here, the authors show that variations in mitochondrial DNA, detectable at birth, are also associated with risk of ASD.