Pubertal Timing In Relation To Maternal Passive Smoking During Pregnancy And Pregnancy Risk Factors In Primary And Middle School Students In Shanghai

Objectives:To estimate the prevalence and determinants of passive smoking in pregnancy; examine whether passive smoking during pregnancy is associated with an earlier age of menarche in offspring; evaluate the relationship between the passive smoking and the adverse pregnancy outcomes. And find out whether adverse pregnancy outcomes have effect on pubertal timing.Methods:Using a stratified cluster sampling method, grade two to five (elementary school), one to three (middle school) and two to three (high school) students were randomly selected to participate in the survey. A total of 1444 students (693 boys and 751 girls), ranging from 8 to 20 years old, were asked to complete a questionnaire. The survey measured pubertal development stages (including breast, pubic hair and armpit hair development stage in girls, bilateral testicular volume, external genitalia, pubic hair, armpit hair and beard development stage in boys, respectively) as well as physique and body fat level (including height, weight). For each participant, information about socio-demographic data, the status of menarche/spermarche, birth weight, gestational weeks, mother’s age of menarche, diet and exercise during the period of investigation were recorded.The investigators involved in the examination are graduate female Child and Adolescent Health majors, who underwent a standardized training prior to the study. Participants were asked if their mothers had been exposed to passive smoke during gestation ("passive smoking" was defined as exhaled smoke or smoke from cigarette ends that non-smokers inhale from active smokers, for>=1 day a week, and>=15 min each time) Data obtained in this current study were analyzed using the probability unit regression method. Participants were asked their actual age and if they were currently having their periods. Based on the data obtained, the proportion of participants within each age group who had experienced menarche increased with age (within the age group). A plot of age vs incidence of menarche revealed an S-shaped curve, and if the log of the median age in each group was plotted against the incidence of menarche using probit analysis, the two show a nearly linear relationship. The regression formula can be calculated using the method of least squares and applied to estimate the median age at menarche. All data were input into Epidata3.1 and analyzed using the SPSS 16.0 package. A two-tailed p-value of less than 0.05 was considered statistically significant. We examined bivariate associations between maternal passive smoking status during pregnancy and prenatal and early life variables using ANOVA for continuous variables and chi-square test for categorical variables. Age at menarche was calculated using the probability unit regression method. Logistic regression models were applied to examine the unadjusted and adjusted associations between prenatal tobacco smoke exposure、maternal pregnancy risk factors and age at menarche in daughters.Results:A total of 1444 students participated in the survey; among which were 693 males, mean age 12.55±3.22 years; and 751 females, mean age 12.87±3.32 years. Birth weight:males 3.7±2.35kg; females 3.55±2.39kg. Birth length:males 50.22±7.67cm; females 50.09±6.98cm.350 of the females had experienced menarche, mean age 12.42±1.1 years. About 16.4% of pregnant women in a passive smoking environment. Maternal exposures to smoke was found to be associated with more newborn female child(P<0.05)、not full term infant(P<0.05).In addition mothers who were smoked during pregnancy were get higher risk of malnutrition (P<0.05), oligohydramnios(P<0.05), placental abruption(P<0.05).As a whole, families whereby pregnant mothers were exposed to passive smoke were of lower economic status than those who were not (p=0.032); fathers had lower educational levels (p<0.001), and higher probability of smoking (p<0.001); mothers were of younger age (p=0.004), and at higher risks of miscarriages (p<0.001). No identifiable associations existed with maternal educational levels or pre-gestational.Effect of passive smoking on offspring: affects birth weight (p=0.021), but no statistical significance exists between passive smoking and present height and weight or length of menstrual cycle of offspring.The average age at menarche was calculated using the probability unit regression method. The average age at menarche of girls whose mothers were exposed to passive smoke during pregnancy was 13.02 years (95% CI:12.66-13.39); and 13.17 years (95% CI 12.77-13.58) in those whose mothers were not exposed to passive smoke while pregnant. The results reflected a difference of about two months in age at menarche between daughters whose mothers were exposed to passive smoking while pregnant versus those who were not; however, this result is not statistically significant.Influence of maternal passive smoking on the age at menarche of daughters:from the logistic regression models of the association between passive smoking during pregnancy and a younger age at menarche (>12 years vs.<12 years). The unadjusted odds ratio (OR) for the association between prenatal tobacco smoke exposure and younger age at menarche was 1.839 [95%CI:1.051-3.22] compared with no exposure. The OR after adjusting solely for maternal age at menarche was 1.841 [95% CI: 1.049-3.231]; 2.043 [95% CI:1.123-3.717] after adjusting for birth weight, birth length and maternal age at menarche; and 2.027 [95% CI:1.109-3.704] after controlling for birth weight, birth length, maternal age at menarche, present weight and height. All OR values are close to 2.There is no significant result between adverse pregnancy outcomes and pubertal timing.Conclusion:Maternal passive smoking not only harms fetal health, but also affects the reproductive health of offspring. Although active cigarette smoking during pregnancy is on a downward trend, maternal passive smoking is on the rise, and most pregnant mothers are unwary of the potential damage that could be caused, leading to a lack of proactive behaviors to avoid tobacco smoke exposure. As such, there is a pressing need for further studies on the promotion of health education on the harmful effects of tobacco smoke.