[Reliability of self-reported maternal smoking during early lactation period]

Smoking cigarettes is very common among lactating women. The objective evaluation of an exposure to cigarette smoke is needed, as cotinine concentration. On many research a questionnaire is the only determinant of fact and intensification of smoking. The aim of this research was to establish a reliability of the questionnaire concerning cigarette smoking among lactating mothers by analyzing cotinine/creatinine ratio.

In 51 lactating mothers (participants of the research on oxidative stress in Obstetrics Departments on 3rd day post partum) during check-up visit, on 30th day post partum a questionnaire concerning smoking cigarettes before, during pregnancy and after childbirth, and amount of cigarettes smoked was made. Samples of matutinal urine were deep freezed in - 700 till cotinine was evaluated immunoenzymatically. Women were divided into groups: I of non-smokers (32 women), II of smokers (19 women). Statistical analysis was made by means of unparametric test U Mann-Whitney.

Average cotinine/creatinine ratio was 33,8 ng/mg in group I; 1275.9 ng/mg in group II. Specificity and sensitivity of data earned by virtue of statement of correspondents was 81% and 89%. Test of cotinine concentration in urine demonstrated 100% sensitivity and 94% specificity compared to the cotinine/creatinine ratio. Directly proportional relationship was stated between amount of cigarette smoked and concentration of cotinine in urine (55.9 ng/ ml cotinine/cigarette).

A questionnaire should not be the only method evaluating smoking among lactating women. The concentration of cotinine shows slightly lower specificity than cotinine/creatinine ratio. Both tests can be dealt equivalent.