2020 Illinois PRAMS Technical Notes

The Illinois Department of Public Health (IDPH) Division of Health Data and Policy collected the 2020 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 46 states, New York City, Washington DC, Puerto Rico, and the Northern Mariana Islands, representing approximately 81% of 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 two to six 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 2020, a total of 1,994 women were selected to participate in the study; 1,205 women completed the survey. Data were weighted and are representative of the 12-month PRAMS-eligible estimated population of 126,199 recent mothers. Data collection in 2020 marks the fifth year of using the Phase 8 PRAMS survey.

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 2020 overall weighted response rate is 61%. The weighted response rates by infant birth weight are 58% for low birth weight and 61% for normal birth weight.

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 percent confidence intervals, and total estimated population affected were calculated using Survey Data Analysis (SUDAAN®) software. Estimates for response categories with small cell size (i.e., respondents <30 in denominator or <6 in numerator) are not reported due to possible imprecision.

PRAMS data are representative of 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.

The Illinois PRAMS project would like to thank all the mothers who participated in our 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 on-going operational and technical support.

This publication was supported by Cooperative Agreement Number 5U01DP006192-05 funded by the CDC. Its contents are solely the responsibility of the authors 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.