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[Validity of the declared tobacco consumption in pregnancy]
M E Castellanos1, M I Muñoz, M Nebot
1Servicio de Ginecología y Obstetricia, Hospital del Mar, Barcelona. 30255mch@comb.es
Objectives:
To analyse the relationship between the stated consumption of tobacco by pregnant women who say they smoked before pregnancy and the levels of cotinine in their urine at the start and end of pregnancy.
Design:
Observational, longitudinal study.
Participants:
During 1997.
Study Group:
147 pregnant women at their first pre-natal visit to outclinics of the Hospital del Mar.
Control Group:
50 non-smoker pregnant women monitored during their pregnancy.
Measurements And Main Results:
The numbers of cigarettes per day that they said they smoked on their first monitoring visit to our centre and at the last attendance before giving birth were recorded. Cotinine levels in the urine samples taken on these visits were measured. Mean cotinine in pregnant women who said they had given up smoking was higher than in non-smokers. There was a statistically significant linear relationship between the number of cigarettes stated and cotinine levels at the first and last pregnancy monitoring visits, as well as between the variation in the number of cigarettes and cotinine levels at these two visits. The negative predictive value of what they said about their tobacco habit was 82.9%.
Conclusions:
There was a certain under-declaration by pregnant smokers, although their statements of consumption and cotinine levels correlated closely. The under-declaration did not increase despite reiterated advice to stop smoking, which means that, despite its limitations, it could be a useful indicator for evaluating the effect of interventions aimed at stopping women smoking during pregnancy.