Page Last Updated: May 11, 2026
Visit Information🔗
Visit Information (table name par_visit_data) includes general visit information (e.g. site and information about missed visits and participant withdrawal), substance use flags, and cohort and caregiver types. The age range of the child participant at each visit is as follows:
| Visit 1 (V01) | Visit 2 (V02) | Visit 3 (V03) | Visit 4 (V04) | Visit 5 (V05) | Visit 6 (V06) | Visit 7 (V07) |
| Prenatal | 0-1 month | 3-9 months | 9-15 months | 10-17 months | 15-30 months | 16-32 months |
Substance Use Flags🔗
Nail biospecimens are not currently included in the SU flag. Users who wish to add nail results into the categorization (consistent with Gurka et al., 2025), please include an ‘or’ statement with the following variables within the nail toxicology table (bio_bm_biosample_nails_results) for visits 1 and 2: c_any_cannabinoid_n (cannabis); c_any_opioid_n (opioid); c_ethanol_n (alcohol); c_nicotine_n (nicotine).
Substance use (SU) flag variables indicate whether a participant met study-defined criteria for prenatal exposure to Alcohol, Nicotine, Cannabis, Opioids, or Stimulants. Variables include instrument-specific and derived SU flags. See Gurka et al., 2025 for full methodological details.
Instrument-specific SU flags are generated from:
- Self-reported use from the Timeline Follow Back (TLFB)
- Diagnosis of NOWSNeonatal Opioid Withdrawal Syndrome or FASFetal Alcohol Syndrome from the Health V2 - Infancy
- Positive toxicology based on Urine biospecimen results (collected at V01 only). Note: Nail toxicology, collected both V01 and V02, is not currently integrated into the SU flags, but will be in the future
Derived SU flags aggregate evidence across instruments to provide a single indicator per substance. With the exception of Stimulants, which do not include a derived flag, a derived SU flag is reported as "Yes" if one or more of the corresponding instrument-specific flags in the summary table below are positive.
SU Flag Variable Summary (For readability, SUFLAG is used as shorthand for the variable prefix par_visit_data_su_flag)
| Substance | Derived SU Flag | Instrument-Specific SU Flags | ||
|---|---|---|---|---|
| Urine | TLFB | Health V2 | ||
| Alcohol | SUFLAG_alcohol |
SUFLAG_bio_bm_ethanol |
SUFLAG_tlfb_bm_alcohol |
SUFLAG_healthv2_ch_fas |
| Nicotine | SUFLAG_nicotine |
SUFLAG_bio_bm_nicotine |
SUFLAG_tlfb_bm_nicotine |
— |
| Cannabis | SUFLAG_cannabis |
SUFLAG_bio_bm_cannabinoid |
SUFLAG_tlfb_bm_cannabis |
— |
| Opioids | SUFLAG_opioid |
SUFLAG_bio_bm_opioid |
SUFLAG_tlfb_bm_opioid |
SUFLAG_healthv2_ch_nows |
| Stimulants | None | SUFLAG_bio_bm_stim |
SUFLAG_tlfb_bm_stimulant |
— |
The thresholds below define when an instrument-specific report is considered positive for prenatal exposure. For each substance, the derived SU flag is positive if one or more of the corresponding instrument-specific reports are positive.
| Substance | Source Instrument | Instrument-Specific Exposure Thresholds |
|---|---|---|
| Alcohol | TLFB | Self-reported use ≥7 standard drinks per week for ≥2 weeks during pregnancy (weeks 3-9) |
| TLFB | Self-reported use ≥3 standard drinks per occasion on ≥2 occasions during pregnancy (weeks 3-9) | |
| Health V2 | Diagnosis of Fetal Alcohol Syndrome (FAS) | |
| Urine | Positive alcohol toxicology result | |
| Opioids | TLFB | Self-reported use of prescribedincluding medications for opioid use disorder or illicit opioids for ≥2 weeks during pregnancy (weeks 3-9) |
| Health V2 | Diagnosis of Neonatal Opioid Withdrawal Syndrome (NOWS) | |
| Urine | Positive opioid toxicology result | |
| Cannabis | TLFB | Self-reported cannabis use for ≥4 weeks during pregnancy (weeks 3-9) |
| Urine | Positive cannabis toxicology result | |
| Nicotine | TLFB | Self-reported nicotine or nicotine product use for ≥4 weeks during pregnancy (weeks 3-9) |
| Urine | Positive nicotine toxicology result |
© Copyright 2025 by Elsevier. All rights reserved. Used/adapted with permission from Gurka et al., Dev Cogn Neurosci. 2025.
Cohort & Caregiver Types🔗
HBCD Cohorts🔗
Cohort information (par_visit_data_cohort) includes cohort subtypes and caregiver type (Type A-E - see details) for each participant. Cohort subtypes are split into Main Child and Multiple Birth, with additional labeling for Postnatal Recruits (PNR) and Multiple Birth siblings (Main Child vs. Sibling):
| Cohort | Cohort Subtype Label | |
|---|---|---|
| HBCD Main Child | HBCD Main Child | |
| HBCD Main Child - Postnatal Recruitment* | ||
| HBCD Main Child - Type A - E | ||
| HBCD Multiple Birth | HBCD Multiple Birth - Main Child | |
| HBCD Multiple Birth - Postnatal Recruitment* | ||
| HBCD Multiple Birth - Postnatal Recruitment* - Sibling | ||
| HBCD Multiple Birth - Sibling | ||
| HBCD Multiple Birth - Type A - E | ||
| * PNR is only available for V02 - see details | ||
Postnatal Recruits (PNR)🔗
Download participant list (available to DUC-authorized users via the HBCD Private Release Notes)
Postnatal Recruits are enrolled in the study after the child is born and complete a modified V01 and V02. The PNR cohort is only denoted for the V02 visit, with all subsequent visits falling under the same cohort as a standard participant. To check if a participant was part of a PNR cohort, users can either check the cohort (par_visit_data_cohort) at V02 or refer to the provided participant list.
Multiple Birth Participants🔗
Download participant list (available to DUC-authorized users via the HBCD Private Release Notes)
Multiple Birth cohorts include siblings/twins enrolled as Main Child and Sibling participants. Certain data fields, such as caregiver or maternal instrument data that are not child-specific (e.g., Adult Demographics), are expected to be identical across siblings. For twins and triplets, all age variables will also be identical, including those derived from jittered date of birth.
The downloadable participant list maps each Main Child to their corresponding Sibling IDs. In the current release, some multiples are incomplete (missing partner ID appears as na in the file):
- 33 Main Child participants do not yet have their paired Sibling included, and
- 4 Sibling participants do not yet have their paired Main Child included.
In the current release, family/maternal-level (i.e. non-child-specific) instrument fields are only populated for the Main Child. These values should be identical for all siblings, and in a future release, HBCD Main Child data will be copied to the sibling profile (e.g. HBCD Multiple Birth - Sibling) for non-child-specific elements so that the information is populated consistently across participants. In addition, a new Data Dictionary element (familyID) will be incorporated to help identify siblings.
Until then, users should obtain non-child-specific values for any Sibling participant by referencing the corresponding Main Child in the mapping file. These data are unavailable for the 4 siblings whose Main Child is not yet included in the release.
Caregiver Types🔗
| Type A | Temporary Alternative Caregiver |
| Type B | Change in Primary Caregiver (Placement Only) Without Change in Legal Custody (But Birth Parent Unable to Complete Visit) |
| Type C | Change in Joint Custody |
| Type D | Child Removed From Birth Parent and Placed in Foster Care (Change in Placement) |
| Type E | Change in Legal Custody and Placement (e.g. adoption) |
References🔗
Gurka, K. K., Burris, H. H., Ciciolla, L., Coles, C. D., Massey, S. H., Newman, S., Rajagopalan, V., Smith, L. M., Zilverstand, A., Bandoli, G., & HBCD Pregnancy Exposures, Including Substances Workgroup. (2025). Assessment of maternal health and behavior during pregnancy in the HEALthy Brain and Child Development Study: Rationale and approach. Developmental Cognitive Neuroscience, 71(101494), 101494. https://doi.org/10.1016/j.dcn.2024.101494