Prenatal smoke exposure and age at Menarche
Initial Award Abstract
This study will examine whether a mother’s smoking during pregnancy affects puberty in her daughter. The marker of puberty that we will use is the age at which the daughter starts menstruating (e.g. age at menarche). Scientific evidence has been accumulating that events during pregnancy, when the baby is developing, can have later effects on health conditions that do not appear until childhood or even adulthood. Recently, there has been much concern that puberty is starting earlier than previously thought among American children, and that this might be due to modern day exposures. Cigarette smoke contains hundreds of chemicals, including some shown to harm reproduction in animals. Smoking is also known to have damaging effects on the development of a baby, causing problems such as low birth weight. Although there is little data addressing potential effects of smoke exposure on puberty, we have been conducting a study that suggests an earlier age at menarche among daughters of smokers. We found these associations to be stronger among children of a race other than White. In general, onset of menarche has been observed to occur at an earlier age among Blacks than Whites. The proposed investigation will make use of data already collected in a large-scale study with a 30-year follow-up, in order to quantify the effect of maternal smoking on early age at menarche, by race.
The data to be analyzed are from the Collaborative Perinatal Project (CPP), a study of over 50,000 pregnant women and their children, conducted in 12 medical centers throughout the United States. Pregnant women were recruited from 1959-1965, their pregnancy outcomes were recorded, and their children were followed for up to 8 years for various health endpoints. Two investigators independently extended the follow-up of sub-sets of the children into adulthood, asking their age at menarche. By combining these two groups, we will have information on 1560 girls born into the CPP. Interviews with their mothers during pregnancy asked about a variety of lifestyle factors, including smoking history. Factors that might bias an apparent effect of smoking on age at menarche are available from the pregnancy interviews and the later childhood exams and interviews. Age at menarche was asked of the daughters as part of the follow-up interview when they were young adults. The mean age at menarche will be calculated, as well as classifying it as “early” (<12) and “late” (>13) ages. These will be compared by amount smoked by the pregnant mother, controlling for related factors. The sub-sets followed include a high proportion of non-Whites (primarily Blacks) so we will be able to examine whether any associations found differ by race, as our earlier work indicated. We will also examine this question by combining this newer data with our previous data.
Given the depth and quality of the data set to be examined, this analysis should yield valuable information about an area deserving further investigation, namely the effects of smoke exposure early in fetal development on later maturation, in a very cost-effective manner. This study will expand our knowledge of the reproductive process and of the effects of smoke exposure during pregnancy on the offspring and their later health. It will also provide guidance for designing future studies of this important issue. |