Thank you for taking the time to fill out this brief online form that will inform our guidance on potential cohort-specific modifications to the analysis plan. This form will solicit the following information:

• Anticipated number of eligible samples
• Whether these samples are from the maternal- or fetal-side of the placenta
• Number of participants in each self-reported race/ethnicity category
• Do you have genetic data to estimate genetic ancestry?
• Number of male and female infants
• Number of low birth weight infants
• Number of high birth weight infants

If both fetal-side and maternal-side samples are available from the cohort, we ask you to please fill out the online form for both sides separately.

This analysis will be restricted to singleton births. If the DNA methylation data stems from a case-cohort study, please restrict the analysis to the sub-cohort. If the DNA methylation data stems from a case-control study, please let us know, and we can discuss the best exclusion criteria to use given the study design that generated the data.

We will not exclude participants based on the incidence of maternal conditions, such as gestational diabetes and preeclampsia, or preterm birth. If placenta DNA methylation and birth size influence the risk of any of these outcomes, adjusting for these factors may introduce collider bias (selection bias), and make it appear there is a relationship between DNA methylation and birth size that is not a true direct effect.

If you have any questions regarding this form, please do not hesitate to reach out to us (Dr. Alexandra Binder; ambinder@hawaii.edu)