title: Folic acid supplementation, dietary folate intake and risk of preterm birth in China.
abstract: OBJECTIVE
  Folic acid supplementation has been suggested to reduce the risk of preterm birth. However, results from previous epidemiologic studies have been inconclusive. We investigated the hypothesis that folic acid supplementation and dietary folate intake during pre- and post-conception reduces the risk of preterm birth.
  
  
  METHODS
  We analyzed data from a birth cohort study conducted between 2010 and 2012 in Lanzhou, China, including 10,179 pregnant women with live singleton births.
  
  
  RESULTS
  Compared to non-users, folic acid supplement users with >12-week duration had a reduced risk of preterm birth (OR 0.67, 95 % CI 0.55-0.83) with a significant dose-response relationship (P for trend = 0.01). A similar pattern was observed for spontaneous preterm birth. Stronger associations were seen for ever use of folic acid supplement and very preterm birth (OR 0.50, 95 % CI 0.36-0.69) and spontaneous very preterm birth (OR 0.42, 95 % CI 0.29-0.63). Dietary folate intake during preconception and pregnancy were also associated with reduced risk of preterm birth (OR 0.68, 95 % CI 0.56-0.83, OR 0.57, 95 % CI 0.47-0.70 for the highest quartiles, respectively), particularly for spontaneous very preterm (OR 0.41, 95 % CI 0.24-0.72, OR 0.26, 95 % CI 0.15-0.47 for the highest quartiles, respectively). There were also decreased risks of preterm birth observed per 10-µg increase in dietary folate intake, and similar associations were found after stratification by folic acid supplementation status.
  
  
  CONCLUSIONS
  Our results suggest that folic acid supplementation and higher dietary folate intake during preconception and pregnancy reduces the risk of preterm birth, and the protective effect varies by preterm subtypes.
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Liu
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Lv
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Hanru
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Yale School of Public Health, 60 College Street, New Haven, CT, 06520, USA.
authors.forename: Nan
authors.initials: N
authors.lastname: Zhao
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Qiu
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: He
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhou
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Xu
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Cui
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Sufen
authors.initials: S
authors.lastname: Liu
authors.affiliation: Yale School of Public Health, 60 College Street, New Haven, CT, 06520, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Lerro
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Lin
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Chong
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Honghong
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Ruifeng
authors.initials: R
authors.lastname: Xu
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Daling
authors.initials: D
authors.lastname: Zhu
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Dang
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Xudong
authors.initials: X
authors.lastname: Han
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Haiya
authors.initials: H
authors.lastname: Bai
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Ya
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Zhongfeng
authors.initials: Z
authors.lastname: Tang
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Ru
authors.initials: R
authors.lastname: Lin
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Yao
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Su
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Wendi
authors.initials: W
authors.lastname: Wang
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Yueyuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Ma
authors.affiliation: Yale School of Public Health, 60 College Street, New Haven, CT, 06520, USA.
authors.forename: Huang
authors.initials: H
authors.lastname: Huang
authors.affiliation: Yale School of Public Health, 60 College Street, New Haven, CT, 06520, USA.
authors.forename: Jiaxin
authors.initials: J
authors.lastname: Liang
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China.
authors.forename: Weitao
authors.initials: W
authors.lastname: Qiu
authors.affiliation: Gansu Provincial Maternity and Child Care Hospital, 143 North Road Qilihe District, Lanzhou, 730050, Gansu Province, China. 2305470816@qq.com.
authors.forename: Qing
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Yale School of Public Health, 60 College Street, New Haven, CT, 06520, USA. yawei.zhang@yale.edu.
authors.forename: Yawei
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002681:China; D015331:Cohort Studies; D004032:Diet; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D015444:Exercise; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage*; D006801:Humans; D039382:Maternal Nutritional Physiological Phenomena; D011247:Pregnancy; D047928:Premature Birth / Q000517:prevention & control*; D012307:Risk Factors; D012959:Socioeconomic Factors; D055815:Young Adult
chemical_list: D005492:Folic Acid
keywords: Dietary folate; Epidemiology; Folic acid supplements; Preterm birth