Methods
Each month approximately 200 mothers who are Missouri residents and recently delivered a live-born infant during the preceding 2-4 months are randomly selected from a file of birth certificate records using a stratified systematic sampling. Mothers, who are mentally incapacitated, have died or had a multiple birth greater than three gestations are excluded from the sample frame. Annual sample size ranges from 1,600 to 2,500. The Missouri PRAMS sample is stratified by infant birth weight (<2,500 grams) are oversampled to permit separate estimates of this subgroup of interest based on adequate sample size.
PRAMS uses three modes of data collection. The initial mode of data collection is a mail survey with an online survey option. Up to three self-administered surveys are mailed to sample women. Women not responding to any of the three mailings are contacted by telephone. The sequence of contacts for PRAMS surveillance is:
1. Pre-letter. This brief letter is sent a few days to one week in advance of the questionnaire. It informs the woman that a survey is forthcoming and offers the option to participate via an online survey by providing a user ID and passcode unique to each woman.
2. First Questionnaire Mailing. The questionnaire is sent with a cover letter that describes the project. Other appropriate materials (e.g., informed consent document, incentive, question-and-answer brochure, resource list, calendar, return envelope) are included as well.
3. Tickler (Reminder Letter). This letter is sent to non-respondents 7-10 days after the questionnaire to remind women to complete the questionnaire and to offer thanks in case the questionnaire was already completed online or returned by mail.
4. Second Questionnaire Mailing. Another questionnaire is mailed one to two weeks after the tickler. A cover letter informs the woman that the previous questionnaire has not been returned and includes a strong appeal for participation. The informed consent document, question-and-answer brochure, resource list, calendar, and return envelope are included with this mailing.
5. Third Questionnaire Mailing (Optional). One to two weeks after the second questionnaire is mailed, a third and final questionnaire is mailed to the woman. A cover letter informs the person that the previous questionnaire has not been completed by web or returned by mail and includes a stronger appeal for participation. The informed consent document, question-and-answer brochure, resource list, calendar and return envelope are included with this mailing. (Missouri PRAMS dropped the third mailing with 2022 data collection)
6. Telephone Follow-up. Seven to ten days after the final mailing, telephone calls are initiated with any non-respondent. Up to 15 telephone calls are made in an attempt to reach the mother and persuade her to complete a telephone interview.
The timing and nature of the mail, web, and telephone contacts is designed to elicit the best response rates possible and to minimize recall bias. To maintain data integrity, the entire data collection period will not exceed 95 days from the date of the pre-letter. The PRAMS Integrated Data Collection System (PIDS) will assist in setting and managing the contact schedule. The Missouri PRAMS survey follows the standardized data collection methodology provided in the CDC PRAMS Model Surveillance Protocol distributed in January 2023. The complete protocol can be accessed at the following web address: http://www.cdc.gov/prams/.
This standardized approach allows for comparisons among states. Multiplying together the sampling, non-response, and non-coverage components of the weight yields the analysis weight. The weight can be interpreted as the number of women like herself in the population that each respondent represents. Analyzing PRAMS data needs to take into account analysis weight and complex sampling designs. Data presented in Missouri PRAMS dashboard and other types of publications are weighted to provide estimates representative of Missouri resident women who have recently delivered a live birth.