关键词: 出生体质量, 叶酸, 复合维生素B, 多水平分析

Abstract: Objective　To analyze the correlation between folic acid and vitamin B complex during the peri-conception period and the neonatal birth weight by multilevel model.Methods　From August to November 2013,stratified,multistage and random sampling method was used to investigate 15-49 aged pregnant women in 2010 to 2013 in Shaanxi province.A self-designed questionnaire was utilized.The questionnaire included the birth date and gender of newborns,gestational age,birth weight,women’s sociodemographic characteristics,history of gestation,pregnant health care,lifestyle of pregnant,and health conditions of pregnant.Women were divided into groups according to their nutrient compliance conditions during the peri-conception period.Women taking folic acid and vitamin B complex,including vitamin B1,B6 and B12,were classified into group A.Women taking folic acid only during the peri-conception period were classified into group B.Women who did not take any of these two during the peri-conception period were classified into group C.Multilevel model was conducted to analyse the relationship between folic acid and vitamin B complex supplementation during peri-conception period and the neonatal birth weight.Results　A total of 26 756 women were included in this study.Group A included 2 441 women（9.12%）,group B included 15 989 women（59.76%）,and group C included 8 326 women（31.12%）.The differences among all groups in terms of the ratio of gestational age<37 weeks and incidence rate of hypertensive disorders complicating pregnancy were not statistically significant（P>0.05）.The differences among all groups concerning gender and birth weight of newborns,childbearing age,culture degree,residence,work condition,household wealth index,primiparity,gestational weeks of first antenatal examination ≤13 weeks,examination times during pregnancy being less than 5 times,iron supplements uptake during peri-conception period,ratios of passive smoking,and incidence rate of anemia for pregnant women were statistically significant（P<0.05）.After correcting the confounding factors,the multilevel model analysis results compared with group C indicated that the birth weight of newborns in group A increased by 37 g on the average,whereas that in group B increased by 22 g,and the differences were statistically significant（P<0.05）.Compared with that of group B,the birth weight of group A increased by 16 g on the average;the difference was not statistically significant（P=0.146）.Conclusion　Taking folic acid during the peri-conception period can help increase the birth weight of newborns.Vitamin B complex exerts no influence on the birth weight of newborns.

Key words: Birth weight, Folic acid, Vitamin B complex, Multilevel analysis