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2021 Illinois PRAMS Technical Notes
Collection of Data
The Illinois Department of Public Health (IDPH) Division of Health Data and Policy collected the 2021 Illinois Pregnancy Risk Assessment Monitoring System (PRAMS) data. Illinois uses the standardized data collection methods developed by the U.S. Centers for Disease Control and Prevention (CDC). These methods are used in 50 jurisdictions representing approximately 81% of all live births in the U.S. Data are collected through mailed surveys with telephone follow-up for non-respondents. In Illinois, a systematic stratified random sample of approximately 180 mothers is selected monthly from a frame of eligible birth certificates. At 2 to 6 months after delivery, the PRAMS program mails an introductory letter and survey to each sampled mother. The program follows up with those who do not initially respond, sending them a reminder letter and two additional survey mailings. PRAMS interviewers telephone mothers who do not respond to any of the mailed surveys to administer the survey by telephone. Surveys are available in English and Spanish, and telephone interviews are conducted in both languages.
In 2021, a total of 1,975 women were selected to participate in the study; 1,119 women completed the survey. Data were weighted and are representative of the 12-month PRAMS-eligible estimated population of 124,709 recent mothers. Data collection in 2021 marks the sixth year of using the Phase 8 PRAMS survey.
Sampling Design
A systematic stratified random sampling design is used to oversample low birthweight (less than 2,500 grams) births. The sample is stratified by low birthweight (less than 2,500 grams) and normal birthweight (2,500 grams or greater). The 2021 overall weighted response rate is 56%. The weighted response rates by infant birthweight are 58% for low birthweight and 56% for normal birthweight.
Weighting and Interpretation of Results
Statistics are based on weighted data. CDC developed the weights to adjust for sample design, non-response patterns, and omissions from the sampling frame. The final sampling weight used to analyze the survey data is the product of these three elements. Weighting is necessary to give unbiased estimates of population parameters.
The percentages, 95% confidence intervals, and total estimated population affected were calculated using Survey Data Analysis (SUDAAN®) software. Estimates for response categories with small cell sizes (i.e., respondents <30 in the denominator or <6 in the numerator) are not reported due to possible imprecision.
PRAMS data represent Illinois resident women, age 14 years or older, who gave birth in Illinois to live infants. The sampling design is valid at the state level and not intended or developed to represent sub-state geographies or their populations without further evaluation. The data are not applicable to all pregnant women. At the direction of IDPH legal counsel, women younger than 18 years of age were not asked questions about physical abuse.
Acknowledgements
The Illinois PRAMS project would like to thank all the mothers who participated in the survey. These women provided valuable information to improve the understanding of why some babies are born healthy and some are not. The Illinois PRAMS project also would like to thank the CDC PRAMS team for their ongoing operational and technical support.
This publication was supported by Cooperative Agreement Number U01DP006627-01 funded by the CDC. Its contents are solely the authors' responsibility and do not necessarily represent the official views of the CDC or the U.S. Department of Health and Human Services.
Call 866-643-7194 with questions about Illinois PRAMS or email dph.pramtrac@illinois.gov.
