This study is an analysis of data collected between 2020 and 2023 in Cycle 1 of the ECHO cohort, a US national, multisite, prospective longitudinal cohort assembled with the aim to improve knowledge of early environmental factors that influence child health and development. We included pregnancies from the ECHO cohort in which live birth occurred at ≥37 weeks and 0 days of gestational age based on best available obstetric dating information available, had placental histopathologic data available, and had at least one Ages & Stages Questionnaire-Third Edition (ASQ-3) completed by a parent between 2 and 18 months of life. We excluded multifetal gestations, pregnancies with uncertain pregnancy dating or a severe fetal malformation(s), and children diagnosed with hypoxic-ischemic encephalopathy or a chromosomal or other genetic condition.

Of 5 ECHO sites that collected placental data in Cycle 1, this analysis included 3 study sites: Childhood Allergy and the Neonatal Environment, Safe Passage Study, and The New York University Children’s Health and Environment Study. The Boricua Youth Study cohort had placental histopathologic evaluation and ASQ-3 data available for 12 maternal-child dyads, but was excluded from this analysis due to small sample size ( Figure ). The Fair Start Study birth cohort had placental data available from 97 additional pregnancies, but did not perform ASQ-3 assessments.

Participant flow diagram

Flow diagram of ECHO cohort participants included in the analytic cohort.

ECHO , Environmental Influences on Child Health Outcomes.

The study protocols were reviewed and approved by the ECHO Institutional Review Boards (local or central). All participants provided written informed consent. The Institutional Review Board at Johns Hopkins Bloomberg School of Public Health approved the involvement of the ECHO Data Analysis Center.

Exposures of interest were chronic placental inflammation, maternal acute inflammatory response, fetal acute inflammatory response, maternal vascular perfusion, and fetal vascular malperfusion. At the selected ECHO cohort study sites, placenta samples were obtained at birth according to their local protocol, ^,, fixed in formalin, then shipped to the ECHO cohort’s center for processing. Hematoxylin and eosin–stained slides were prepared and reviewed centrally by an experienced perinatal pathologist (C.S.). Eight sections of the placental disc, 2 in each quadrant, were taken to maximize sensitivity, in addition to 2 samples from the umbilical cord, 2 samples directly under the placental cord insertion site, 2 membrane rolls, and one additional sample taken from any gross lesions. Histopathologic lesions were identified in accordance with the Amsterdam Placental Workshop Group Consensus Statement and coded as present or absent. Chronic placental inflammation was defined as the presence of one or more of the following 6 histopathologic lesions: (1) chronic deciduitis (ie, plasma cell infiltrates present in the decidua), (2) chronic chorioamnionitis (ie, lymphoplasmacytic infiltration of the chorion and amnion), (3) basal chronic villitis (ie, infiltration of anchoring villi attached to the basal plate by lymphocytes, histiocytes, and/or plasma cells) (4) chronic chorionic vasculitis (ie, eosinophilic T-cells seen crossing fetal vessels in the chorionic plate), (5) chronic villitis of unknown etiology (ie, infiltration of fetal stem villi by lymphocytes, histiocytes, and/or plasma cells), and (6) chronic chorionitis (ie, lymphocytic or lymphoplasmacytic infiltration of the chorionic plate alone). ^, Maternal acute inflammatory response was defined as the presence of neutrophils in the extraplacental membranes and/or chorionic plate, whereas fetal acute inflammatory response was defined as the presence of neutrophils in the umbilical cord and/or chorionic plate vessels. Maternal vascular malperfusion was defined as the presence of accelerated villous maturation or decidual arteriopathy, intervillous thrombi, villous infarcts, and/or chronic or acute abruption within the placenta. Fetal vascular malperfusion included the presence of avascular villi, villous stromal vascular karyorrhexis, hemorrhagic endovasculitis, fetal stem villous mural thrombosis, and/or fetal large vessel mural thrombosis in the chorionic plate vessels.

Each study site administered the ASQ-3 questionnaire, completed by the child’s birthing parent typically within 10 to 15 minutes, to screen children for risk of abnormal early childhood neurodevelopment in the first 18 months of life. The Childhood Allergy and the Neonatal Environment and Safe Passage Study sites administered the ASQ-3 in English only; New York University Children’s Health and Environment Study administered the ASQ-3 in English, Spanish, and Chinese. The primary outcome was an abnormal, or high-risk, composite ASQ-3 screen, defined as having a high-risk score on at least one of the 5 individual domains (communication, gross motor, fine motor, personal-social, and problem-solving) on any ASQ-3 questionnaire completed between 2 and 18 months of life. The individual ASQ-3 domains were secondarily assessed, also as binary outcomes (high-risk vs low-risk screen). A high-risk score was defined as greater than or equal to 2 standard deviations below the mean; all other scores were considered low-risk. If a child had multiple ASQ-3 questionnaires completed over this period, the lower score was used for the composite and individual domain scores.

Each ECHO cohort site collected covariate information, which was harmonized by the ECHO Data Analysis Center. We identified potential confounders and precision variables for consideration in analytic models based on expert input and literature review. We considered the following variables as potential covariates for adjustment: site, maternal age at delivery, highest level of maternal education, health insurance (public, private, or both), family structure, prenatal tobacco, alcohol or other substance use during pregnancy, maternal depression or anxiety (at any point prepregnancy, during pregnancy, or through 8 weeks postpartum by medical records or self-report), parity, antenatal corticosteroid exposure, delivery indication (spontaneous or medically indicated), group B streptococcus status, child sex, and neonatal birthweight. Based on data availability, the following variables were included in the final multivariable model: maternal age at delivery, highest level of maternal education, insurance, maternal depression, parity, child sex, and neonatal birthweight. Neonatal birthweight was included as a precision variable given that low birthweight, fetal growth restriction, and/or small-for-gestational age (SGA) is not always related to placental dysfunction and may be constitutional in approximately 20% of cases. Yet, birthweight has been identified as an important prenatal factor associated with abnormal early childhood neurodevelopment. ^,,,, Although we report the distributions of hypertensive disorders (chronic hypertension, gestational hypertension, or preeclampsia), prepregnancy body mass index (both as a continuous and categorical measure), and pregestational or gestational diabetes in the analytic cohort, these maternal factors were not included as covariates as they may contribute to placental histopathology. ^,,,,, We additionally report on paternal age, self-reported maternal race and ethnicity, annual household income, gestational weight gain, gestational age at birth, mode of birth (vaginal or cesarean), neonatal birthweight percentile (SGA, birthweight <10%; large-for-gestational age, birthweight >90%), and 5-minute Apgar score.

We report descriptive statistics of all demographic and clinical characteristics for the overall cohort and for each individual cohort. Pearson’s Chi-square or one-way analysis of variance tests, as appropriate, were used to compare baseline characteristics across the 3 included cohorts. Additionally, we report the median (interquartile range) child age at the time of completion of the ASQ-3 questionnaire. For each placental histopathologic exposure, the proportion of children with, compared to those without, the primary composite and individual secondary outcomes was assessed using Pearson’s Chi-square test. We further report the proportion of low-risk and high-risk ASQ-3 screens in ECHO participants with at least one ASQ-3 assessment performed at 2 to 18 months regardless of availability of placental exposure data with those in the analytic subset.

Using generalized estimating equation regression models with a binomial link function and clustering based on ECHO cohort study site, univariable and multivariable analyses were performed to generate the covariate unadjusted and adjusted odds and 95% confidence intervals (CIs), respectively, of a child having a high-risk vs a low-risk screen for the primary and secondary outcomes based on the presence of each placental histopathologic exposure. We imputed missing covariates using multiple imputation by chained equations with 10 imputed datasets and 5 iterations. Univariate and multivariable analyses were repeated in a prespecified sensitivity analysis evaluating only the subset of children who were appropriate-for-gestational age with respect to size at birth (ie, neonatal birthweight 10th–90th percentile) according to the INTERGROWTH-21st fetal growth standards to exclude SGA infants given heterogeneous factors associated with early childhood neurodevelopment in the SGA population. ^,,,

We further conducted a sensitivity analysis excluding individuals with prepregnancy body mass index ≥30 kg/m ² to exclude any potential influence of obesity given the established links between maternal obesity and placental inflammation. ^, Based on expert recommendation, clinical differences observed in early childhood development by child age, and improved validity of the ASQ-3 in children at older testing ages, we then examined models stratified by age at ASQ-3 assessment (<12 vs 12–18 months). ^, As offspring sex differences have been associated with differential risk of adverse pregnancy and child neurodevelopmental outcomes, with greater morbidity observed among males, we separately examined models stratified by child sex (male vs female). ^, Finally, we performed univariable and multivariable regression models using generalized estimating equations for all outcomes based on exposure to each of the 6 individual histopathologic subtypes of chronic placental inflammation.

All statistical analyses were conducted using R (version.4.4.0; R Core Development Team). A P value <.05 was used to determine statistical significance. Due to the exploratory nature of this analysis, correction for multiple comparisons testing was not performed.