Women who remember, women who do not: a methodological study of maternal recall of smoking in pregnancy.

Introduction: Retrospective recall of smoking during pregnancy is assumed to be substantially biased, but this has rarely been tested empirically.
Methods: We examined the validity of an interview-based retrospective recall more than a decade after pregnancy, in a cohort with repeated, multimethod characterization of pregnancy smoking (N = 245). Retrospective smoking patterns were examined in relation to prospective reported and biological estimates of overall and trimester-specific smoking status and intensity. We also compared characteristics of women whose smoking status was misclassified by either prospective or retrospective measures with women whose status was congruent for nonsmoking across timepoints.
Results: In general, sensitivity and specificity of recalled smoking were excellent relative to both prospective self-reported and cotinine-validated smoking status and trimester-specific intensity. However, measures were less congruent for amount smoked for women who recalled being heavy smokers. Further, retrospective measures captured some smokers not identified prospectively due to smoking that occurred prior to assessments. Women who would have been misclassified as nonsmokers based on either prospective or retrospective assessment differed significantly from congruently classified nonsmokers in a number of maternal, family, and neighborhood, but not child behavior, characteristics.
Discussion: When epidemiological studies of the impact of smoking in pregnancy use retrospective methods, misclassification may not be a significant problem if prenatal smoking is assessed in terms of the pattern across pregnancy. This type of interview-based recall of pregnancy smoking may be relatively accurate, although optimal measurement should combine retrospective and prospective self-report and biological assays, as each provide unique information and sources of error.