Recall of age of weaning and other breastfeeding variables.
BACKGROUND
Many studies of the impact of breastfeeding on child or maternal health have relied on data reported retrospectively. The goal of this study was to assess recall accuracy among breastfeeding mothers of retrospectively collected data on age of weaning, reasons for cessation, breast pain, lactation mastitis, and pumping.


METHODS
Women in Michigan and Nebraska, U.S.A. were interviewed by telephone every 3 weeks during the first 3 months after the birth of their child, and mailed a questionnaire at 6 months. A subset was interviewed again by telephone approximately 1-3.5 years after the birth. The results for the three recall periods, collected 1994-1998, were compared using correlation, linear and Cox regression analysis, and sensitivity and specificity estimates.


RESULTS
The 184 participants were aged 18-42, mostly white (95%) and 63% had an older child. The age of weaning tended to be overestimated in interviews 1-3.5 years after birth compared to those within 3 weeks of the event, by approximately one month for 1-3.5 year recall and two weeks for 6-month recall (p < 0.001 in both cases). Recall accuracy of reasons for weaning varied greatly by reason, with mastitis and return to work having the most recall validity. The sensitivity of 1-3.5 year recall of mastitis was 80%, but was only 54% for nipple cracks or sores.


CONCLUSIONS
Breastfeeding duration among short-term breastfeeders tended to be somewhat overestimated when measured at 1-3.5 years post-partum. Reporting of other breastfeeding characteristics had variable reliability. Studies employing retrospective breastfeeding data should consider the possibility of such errors.
Gillespie
Brenda
B
Center for Statistical Consultation and Research, University of Michigan, Ann Arbor, MI 48109-1070, USA. bgillesp@umich.edu
d'Arcy
Hannah
H
Schwartz
Kendra
K
Bobo
Janet Kay
JK
Foxman
Betsy
B