Data Methodology

Where the data comes from

The PRAMS sample of women who had a recent live birth is drawn from the jurisdiction's birth certificate file. Each participating site samples between 1,000 and 3,000 women annually. Women from some groups are sampled at a higher rate to ensure adequate data are available.

Data collection methods

Detailed PRAMS methodology

PRAMS uses standardized data collection procedures and instruments. This is to allow for comparisons among jurisdictions and optimal use of the data for single-jurisdiction or multi-jurisdiction analysis. However, each jurisdiction (or site) can customize certain portions of the protocol.

The principles and practices of mail/telephone survey methodology used by PRAMS are based primarily on the research of Don Dillman.¹ A key aspect of this approach is to make numerous and varied contacts with sampled mothers.

PRAMS uses three modes of data collection. Surveys can be completed by mailed questionnaire, telephone interview, and, starting with the 2023 birth cohort, online, using a web survey module. Selected women are first contacted by mail. If there is no response to repeated mailings, they are contacted and interviewed by telephone.

Each month at the jurisdiction level, a stratified sample is randomly drawn from the current birth certificate file. For each of these monthly samples, or "batches," a series of mailings begins 2 to 4 months after delivery. This is to allow new mothers time to respond to questions about the early postpartum period. With all mailings, an invitation is sent to complete the survey by web.

Telephone follow-up begins for nonrespondents after the mailing of the last questionnaire packet. The calling period continues for 2 to 4 weeks, and up to 15 calls are made for each viable telephone number.

Additional information on PRAMS methodology can be found here: The Pregnancy Risk Assessment Monitoring System (PRAMS): overview of design and methodology.

The PRAMS Questionnaire

The original PRAMS questionnaire was developed in 1987. Topics addressed in the PRAMS survey include: preconception, prenatal, and postpartum care; obstetric history; maternal substance use; physical abuse; contraception; economic status; maternal stressors; and early infant development and health status. Learn more about the questionnaires and download the latest PRAMS questionnaires.

How the data is evaluated

PRAMS Weighting Process

Each participating PRAMS site has a unique sampling approach. Thus, the data are weighted by jurisdiction. PRAMS aggregate data are not weighted to provide national estimates.

Each jurisdiction draws a stratified random sample of 100 to 250 new mothers monthly from a frame of eligible birth certificates. Sampling plans are tailored to each site's research and programmatic needs. PRAMS sites identify stratification variable(s) of interest for oversampling of sub-population(s). Commonly used stratification variables include: birth weight; maternal race and ethnicity; Medicaid status; and geography.

Survey responses are linked to select birth certificate information to create the data set for analysis. The PRAMS data set contains demographic and clinical information collected through each jurisdiction's vital records system. This birth certificate information is the basis for the random drawing of survey participants. This allows for generalization of results to each jurisdiction's entire population of births by using sampling, nonresponse, and noncoverage weights.

Analyzing PRAMS data requires special statistical software that accounts for the complex sampling designs that are used.