Two-Year Test-Retest Reliability of the Breastfeeding Duration Question Used By the Pregnancy Risk Assessment Monitoring System (PRAMS): Implications for Research.

Recent literature on this topic from high-income countries falls into two categories: entirely retrospective versus "prospective" reliability assessments. Entirely retrospective assessments (both inquiries occur well after weaning) universally report exceedingly high reliability, whereas "prospective" assessments (women report infant feeding behavior during infancy, immediately after weaning, and some years later are asked to replicate their original answer) universally report poorer reliability. Interestingly, all "prospective" reliability studies, including ours, found that women over-report past breastfeeding durations by about 1 month upon the second inquiry. Researchers need not refrain from using maternal self-reported breastfeeding durations, because participants are largely still ranked correctly, relative to each other. However, such research efforts must avoid attempting to determine any optimal threshold duration.