[Effect of cigarette smoking on blood lead levels in pregnant women]

Abstract

Tobacco smoking creates health problems which apply not only to individuals and the family but also to different ages and social groups, as well as the national economy. Epidemiologic studies conducted at the Institute of Mother and Child indicated that in Poland 25-30% women smoke during pregnancy. Lead exposure from cigarette smoke may have a negative effect on the transplacental flow of micronutrients and have an adverse influence on the growth and development of the fetus, and then on children. The aim of this study was to estimate the effect of smoking cigarettes on plasma and whole blood lead levels in pregnant women.

Material and methods: Eighty healthy pregnant women, patients of the Clinical Department of the Obstetrics and Gynecology Institute of Mother and Child and Warsaw Medical University, were divided into two groups: group I - tobacco smokers and group II- tobacco abstainers according to questionnaire declaration and serum cotinine concentration. Current smokers were defined as those who had smoked 5 cigarettes per day for 2 years before conception and continued smoking during pregnancy. The women exposed to environmental tobacco smoke (smoking spouse or other family members, co-workers) were excluded from the non-smoking group. All pregnant volunteers signed a written, informed consent form, approved by the Institute's Ethical Committee. The concentrations of lead in plasma and whole blood were analyzed using inductively coupled plasma mass spectrometry on spectrometer analyzer ICP MS Elan 6100 (Perking Elmer, Germany). Levels of cotinine in serum were determined by Cotinine Direct ELISA test (Calbiotech Inc. Canada).

Results: In the group of smoking mothers the mean serum cotinine concentration was 69.1 μg/L, whereas in the group of tobacco abstainers it was present only in trace amount. In group I we observed a significant positive correlation between serum cotinine and the number of cigarettes smoked daily (r=0.74; p<0.001), as well as the period of smoking before conception (r=0.60; p<0.001). The concentrations of lead in the plasma of smoking women were significantly higher than in the group of tobacco abstainers in each trimester of pregnancy (I trimester: 0.22 μg/dL vs 0.12 μg/dL p<0.01; II trimester: 0.19 μg/L vs 0.10 μg/L p<0.001; III trimester 0.28 μg/ dL vs 0.13 μg/dL p<0.0001). Tobacco smoking mothers also had a higher concentration of lead in whole blood as compared to pregnant non-smoking women. These differences were statistically significant and amounted to 2.15 μg/dL vs 1.28 μg/L in the first, 1.99 μg/dL vs 1.19 μg/dL in the second and 2.11 μg/dL vs 1.58 μg/dL in the third trimester of pregnancy. We observed that the level of lead was correlated with cotinine in blood, as well as with the number of cigarettes and the length of time women smoked before conception. Such an effect was observed in every trimester of gestation. A strong correlation between the number of cigarettes/day and lead concentration in plasma (r=0.57; p<0.001) and whole blood (r=0.54; p<0.001) was found in the third trimester of pregnancy.

Conclusions: Tobacco smoking during pregnancy increased the concentrations in maternal blood lead. The level of lead in plasma and whole blood correlated with the degree of intensity of cigarette smoking in the pregnant women studied. It may be a result of influencing the mobilization of calcium from the bone with simultaneous release of lead deposited in the bone. Further studies are required to characterize the effect of higher lead level in the blood of mothers on the risk of premature labor, low birth weight of newborns and their inferior development.