The Heartland Study will examine the effects of prenatal maternal herbicide exposures on pregnancy outcomes and childhood development. We will do so by assessing whether higher herbicide exposures during pregnancy are associated with more frequent and/or more serious reproductive problems, adverse birth and developmental anomalies.
Urinary levels of herbicides, include glyphosate, 2,4-D, dicamba, and atrazine, will be calculated for all enrolled mother-infant pairs (MIPs). Epigenetic changes (often called epimutations) will be studied in buccal cells swabbed from the inside of the cheek of moms and babies in an effort to correlate markers of epigenetic change to altered health and developmental outcomes.
Researchers will review medical charts and administer questionnaires so they can observe, document, and better understand:
- Maternal, neonatal and pediatric health outcomes;
- Any maternal risk factors or impacts from pre-existing conditions; and
- Demographic characteristics of the study population.
Several clinical outcome measurements will be collected and assessed relative to herbicide exposure levels, including:
- Pregnancy outcomes and duration;
- Neonatal conditions and growth percentiles; and
- Infant and early child developmental and behavioral milestones.
Subpopulations will be identified based upon maternal risk factors and pre-existing conditions for separate analysis.
Indirect measures of herbicide exposure at two endpoints (just prior to and during pregnancy) will be analyzed and associated with urinary exposure levels. A maternal and paternal study questionnaire will be administered following delivery. Participant responses will be assessed and associated with geographical location of residence, household and work related environments, drinking water sources, food and beverage consumption, as well as reproductive and family medical histories.
Infant and Early Child Development
Newborn infants will be observed and followed at least to age 3 years. Medical charts will be reviewed and infant demographics, developmental progress, conditions/diagnosis, and illnesses will be recorded.
With parental consent, infants will be scheduled for child developmental assessments at ages 1, 2 and 3 years, whenever possible. Standardized assessment tools such as motor and cognitive screens, and ADHD and autism screens will be used and interpreted by professionals specialized in child development.
Physiological measures and development will also be recorded and tracked including child growth, hospitalizations, blood pressure, and BMI. An inventory of child health and well-being will be surveyed and recorded at each age interval. If funding permits, children’s urine will be collected during developmental clinical visits, when and as possible, and measured for herbicide levels.
The Heartland Study will assess potential herbicide-induced epimutations that may be heritable and a contributing factor in developmental problems and the onset of disease. Buccal cells are a single cell type that has been used to identify epimutations in prior studies.
We will strive to collect maternal samples at each pregnancy trimester, as well as a neonatal sample following delivery. In addition, additional buccal samples will be collected, to the extent possible, during the child’s annual developmental evaluation, and from other direct relatives (e.g. a paternal sample, grandparent samples).
Baseline Herbicide Metrics
The accuracy of herbicide exposure estimates directly impact the power (i.e. accuracy) of epidemiological studies. This study will calculate and compare several such exposure-related metrics in an effort to generate new, more accurate methods to approximate exposures from measured, urinary levels and herbicide use data. Herbicide use around the home of participants enrolled in the study is likely to have an impact on exposure levels, and will be explored via questionnaires.
Next-generation exposure metrics using remote sensing data and analytical tools are being developed by epidemiologists conducting location-based studies. Pending funding, we will draw upon these tools to estimate metrics of herbicide use intensity in concentric circles of varying diameter, e.g. 0.5, 1.0, and 5 miles, around each participant’s residence.
Using geospatial data and publicly accessible maps of land use and cropping patterns, novel herbicide use metrics will be developed that will allow for detailed exposure estimates.
Tracking herbicide use patterns and exposure levels requires the establishment of baseline and temporal data. Developing detailed datasets useful in estimating trends in both urinary levels and pounds of herbicides applied are key objectives of the Heartland Study. Examples of existing data, and sources of stored urine samples that may be used in building the biomonitoring dataset include:
- NHANES biomonitoring data in pregnant women for 2,4-D;
- National nuMoM2b Nulliparous Pregnancy Outcome Study (2010-2013); and
- Indiana Pregnancy and Environmental Exposure Study (PEES) (2013-2016).
Opportunities are being explored to secure additional, stored urine samples from studies conducted in the 1990s. Stored urine samples will be tested by the same lab, using the same methods, as the prospectively collected urine samples from mother-infant pairs, reducing possible sources of variability and lending confidence in the accuracy of the trends the study will generate.