Smoking habits among pregnant Danish women: reliability of information recorded after delivery.
OBJECTIVE
To compare recall of smoking habits during pregnancy 0.5-3 years after delivery across groups defined by recall time (5 six month periods) and pregnancy outcome (pre-eclampsia, pregnancy induced hypertension, intrauterine growth retardation, preterm or post-term delivery compared with controls).


METHODS
Case-control nested in cohort study.


METHODS
A subsample of 503 women from a cohort of 6347 women established between 1989 and 1991 in Aarhus University Hospital.


RESULTS
Measures of agreement between concurrent and retrospective data on smoking status varied between 0.93 and 1.0 (sensitivity), 0.90 and 0.98 (specificity), and 0.79 and 0.98 (kappa). Spearman's correlation coefficients for number of cigarettes smoked/day varied between 0.87 and 0.97; mean differences were all close to zero. Accuracy of recall tended to diminish with increasing alcohol intake, particularly among women smoking > or = 10 cigarettes/day.


CONCLUSIONS
Information on smoking habits could be accurately obtained retrospectively independent of recall time and the pregnancy outcomes studied here. Accuracy diminished with increasing alcohol intake, particularly among heavy smokers.
Department of Obstetrics and Gynaecology, Aarhus University Hospital, Denmark.
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D016022:Case-Control Studies; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006306:Health Surveys; D006801:Humans; D015233:Models, Statistical; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D011256:Pregnancy Outcome; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012907:Smoking / Q000453:epidemiology*