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Smoking during pregnancy: chromosome damage in newborns

Institution: Lawrence Livermore National Laboratory
Investigator(s): James Tucker, Ph.D.
Award Cycle: 1999 (Cycle 8) Grant #: 8RT-0070H Award: $1,662,871
Subject Area: Epidemiology
Award Type: Research Project Awards

Initial Award Abstract
The purpose of this proposed work is to improve our understanding of the health risks to newborn babies and their mothers caused by smoking during pregnancy. When pregnant women smoke, chemicals from the smoke enter their blood, then cross the placenta and enter the baby's blood. Many of the chemicals found in cigarette smoke are known to cause genetic damage and cancer. It is possible, then, that smoking during pregnancy increases babies' genetic damage, and may increase these babies' chances of getting cancer when they are older. Because most forms of cancer take many years to develop, smoking during pregnancy may significantly affect the health of these babies when they become adults. Our present level of knowledge, however, is not sufficient to know whether this is really true. Nor do we know whether the genetic make-up of some babies and their mothers puts the babies at an increased risk of smoking-related cancer compared to other babies.

We have performed two small, preliminary studies like the larger study proposed here. In the first study we showed that adults who smoke 2 packs of cigarettes per day accumulate genetic damage at a rate that is 30% higher than in non-smokers. In the second study we obtained umbilical cord blood from 14 newborns whose mothers smoked during pregnancy, and we compared the amount of chromosome damage to 40 babies whose mothers did not smoke during pregnancy. Babies whose mothers smoked during pregnancy had more than twice as much genetic damage as babies whose mothers did not smoke during pregnancy, even though these mothers all smoked less then 2 packs per day. The larger increase in genetic damage in these babies suggests that they may be more susceptible than adults to the adverse genetic effects of smoking. Interestingly, the type of genetic damage we found in both studies was similar to that seen in many kinds of cancer cells. This suggests, but does not prove, that babies whose mothers smoked while pregnant may have a greater chance of developing cancer. Further work is needed before we can know for certain whether this is true.

We propose to perform a larger and more detailed investigation that will extend these earlier efforts. If the results of this larger study also show an increase in genetic damage in babies whose mothers smoked during pregnancy, then we will be able to state with much greater confidence that smoking during pregnancy is harmful to babies. In this work, we propose to analyze samples of blood from 300 women and placental blood from each of their newborn babies. Each blood sample will be analyzed in three ways. First, we will look at the chromosomes inside the blood cells. Chromosomes are packages of genes, and it is very important to peoples' health that these chromosomes do not become damaged or rearranged because this can cause cancer. To measure chromosome damage, we will stain chromosomes in different colors and look for rearrangements of the colors. Second, some of the blood cells will be exposed to a chemical called bleomycin which will help us identify mothers and babies who may be more susceptible to the effects of chemicals in cigarettes. Finally, the mother of each baby will provide several blood samples during pregnancy so that the level of cigarette-related chemicals can be determined. These chemical assays have been shown to provide a very reliable indication of cigarette use, and are much more accurate than the information obtained by questionnaires.

The public health consequences of this proposed research are expected to be significant. We expect to learn whether mothers who smoke during pregnancy are increasing their child's level of genetic damage, and also possibly increasing their child's risk of getting cancer. This work is also expected to help us identify mothers and newborns who have a higher-than-average risk of developing smoking-related genetic damage. The results may be applied to educational efforts designed to reduce or eliminate smoking by pregnant women. Knowledge gained from this research will enable parents, and especially mothers, to be informed of the risks that smoking poses to unborn children.