Smoking in pregnancy.

Zanardo et al. (2005) raise an interesting issue in their article, namely, the influence of smoking on immunologic parameters and especially on the composition of human breast milk. The findings deserve notice and further investigation.

Because of the importance of the findings, the errors and inconsistencies in the article (Zanardo et el. 2005) should be corrected. The first inconsistency is related to the number of participants: In the "Materials and Methods," Zanardo et el. (2005) gave two different numbers:

   Of the 1,217 eligible participants, 25 of 26 self-identified
   as smokers ([greater than or equal to] 5 cigarettes per day
   through pregnancy until last trimester) were
   recruited for study participation. One was
   excluded from the final analysis because of maternal
   fever. Control participants included consecutive
   women without history of smoking and
   matched a smoking participant on the basis of
   overall inclusion criteria.

   We grouped human milk samples into third
   postpartum day smoker and nonsmoker mother
   groups, with 42 and 40 samples per group,
   respectively, and into 10th postpartum day
   smoker and nonsmoker mother groups, with 42
   and 40 samples per group, respectively.

The latter numbers (42 and 40) are also repeated in the first sentence of "Results" and in Table 1. Also in Table 1 the average number of cigarettes smoked per day by the 42 smokers is given as 3.2 [+ or -] 0.7 (mean [+ or -] SD). This is inconsistent with their selection criterion of "[greater than or equal] 5 cigarettes per day."

Table 1 also provides information on birth weight, gestational age, and APGAR score. As expected from numerous previous studies, the children of the smokers scored lower in all these respects. Under "statistical analysis" the authors write that they "used the Student t-test for the analysis of [these] data." To apply the Student t-test for the birth weight data seems a sensible choice. When doing this using the figures provided in Table 1, the difference of the birth weight between the children of smokers and nonsmokers is clearly highly significant (t = 9.45). In the "Results," Zanardo et al. (2005) stated erroneously that "the birth weight of the newborn infants of smoker mothers was not significantly lower."

Editor's note: In accordance with journal policy, Zanardo et al. were asked whether they wanted to respond to this letter, but they chose not to do so.

REFERENCE

Zanarda V, Nicolussi S, Cavallin S, Trevisanuto D, Barbata A, Faggian D, et el. 2005. Effect of maternal smoking on breast milk interleukin-1[alpha], [beta]-enderphin, and leptin concentrations. Environ Health Perspect 113:1410-1413.

Hanns Moshammer

Manfred Neuberger

Institute of Environmental Health

Medical University of Vienna

Vienna, Austria

E-mail: [e-mail]

The authors declare they have no financial interests.