Analysis Of The Risk Factors Leading To Low Birth Weight And Its Association With Maternal Exposure To Aluminum In WuHan

Objective: Low birth weight is a global public health problem, which covers a wide range and has profound impacts on early life growth and chronic diseases in adulthood. These impacts not only restrict population health and socioeconomic development seriously, but also bring a huge burden on the family and society. The embryonic stage is a sensitive period of the development of life, and is related to many factors like mothers' living habits during pregnancy closely. It is generally known that aluminum is a heavy metal widely applied to our daily life and production.Studies have reported that aluminum will affect fetal intrauterine growth because of its reproductive toxicity. However, the epidemiological evidence on the relationship between maternal exposure to aluminum and low birth weight is not strong enough.Therefor, for preventing the occurrence of adverse prenatal factors and providing scientific advice on antenatal care, we established a case-control study to investigate the association between fetal growth and various factors and aluminum exposure.Method: Matching 1:3 according to the maternal age and newborn's sex, select 158 cases of low birth weight infants and 474 normal birth weight infants, all the neonates were from the Healthy Baby Cohort and born in Wuhan maternal and child health care hospital from November 1, 2012 to April 1, 2014. Low birth weight infant is a singleton living newborn whose body weight less than 2500 g and without birth defects, and normal infant is a single living newborn between 2500-4000 g with no birth defects. The questionnaire were completed by mothers when they were in hospital to collect the basic information of parents, working and living conditions,maternal nutrition during pregnancy, and so on. The neonatal information is collected from the hospital data. Creating the database through Epidata3.1 software, collecting maternal urine sample by professional, the concentration of aluminum in maternal urine sample is detected through ICP-MS and is divided into three grades. The SPSS17.0 software is used to describe basic information. Using the Wilcoxon signed rank test and the conditional logistic regression analysis to find the factors influencing birth weight and analysis the association between urine aluminum concentration and low birth weight.Result: 1. The average age of 632 pregnant women is 28.7 years old. The sex ratio of infants is 0.95(boy: girl). The average gestational week in case group is 36.1 weeks and is 38.9 weeks in control group. The average birth weight in two group is 2252 g and 3310 g respectively.2. The result of multi-factor logistic regression analysis shows that more pregnancy weight gain(OR=1.073, P<0.01), longer gestational week(OR=2.707, P<0.01) are protective factors of low birth weight, and vaginal bleeding during pregnancy(OR=1.981, P<0.05), oligohydramnios(OR=9.175, P<0.01), gestational hypertension(OR=5.271, P<0.01) are risk factors of low birth weight.3. In case-control study, the result of the Wilcoxon signed rank test is Z=3.2715,P=0.0011, indicating that the concentrations of urine aluminum in two groups are different significantly and which in case group is higher than it in control group.4. The concentration of urine aluminum was divided into three grades, and the lowest tertile was assigned as the referent group. The result of conditional logistic regression showed that middle concentration urine aluminum had no significant effect on LBW(OR=1.55, P>0.05), while high concentration urine aluminum had positive correlation with LBW(OR=2.24, P<0.01). 5. Adjusted for other factors from factor analysis, the result was similar to what is un-adjusted: middle concentration urine aluminum had no significant effect on LBW(OR=1.27,P>0.05), the high concentration group had significant influence on LBW(OR=1.31, P<0.05).6. Divided into two groups according to the mother's age, the effects of different concentrations of urine aluminum on LBW in two groups was consistent. Before adjusted for other factors, high concentration aluminum exposure had a positive correlation with LBW in two groups, but the correlation disappeared after adjusted.7. Divided into two groups according to infant gender, the effects of different concentrations of urine aluminum on LBW in two groups was consistent. Before adjusted for other factors, high concentration aluminum exposure had a positive correlation with LBW in two groups, but the correlation disappeared after adjusted.Conclusion: 1. Pregnancy weight gain, gestational week at delivery were protective factors of LBW. Therefor, it is important to strengthen the awareness of health care during pregnancy in pregnant women, and ensure adequate nutrition to prevent fetal growth damage. In addition, it is essential to make the gestational week in normal range in order to avoid miscarriage and premature birth. As the risk factors, vaginal bleeding during pregnancy, hypamnion, gestational hypertension were seriously harmful to fetal development, and should be given enough attention.2. The result of case-control study on embryonic aluminum exposure and LBW reflected that low level exposure to aluminum had no effects on LBW and high level exposure was a risk factor affecting embryo intrauterine growth. So pregnant women should reduce the use of aluminum products and aluminum containing food to minimize adverse hazards.