title: Associations of Maternal Vitamin B12 Concentration in Pregnancy With the Risks of Preterm Birth and Low Birth Weight: A Systematic Review and Meta-Analysis of Individual Participant Data.
abstract: Vitamin B12 (hereafter referred to as B12) deficiency in pregnancy is prevalent and has been associated with both lower birth weight (birth weight <2,500 g) and preterm birth (length of gestation <37 weeks). Nevertheless, current evidence is contradictory. We performed a systematic review and a meta-analysis of individual participant data to evaluate the associations of maternal serum or plasma B12 concentrations in pregnancy with offspring birth weight and length of gestation. Twenty-two eligible studies were identified (11,993 observations). Eighteen studies were included in the meta-analysis (11,216 observations). No linear association was observed between maternal B12 levels in pregnancy and birth weight, but B12 deficiency (<148 pmol/L) was associated with a higher risk of low birth weight in newborns (adjusted risk ratio = 1.15, 95% confidence interval (CI): 1.01, 1.31). There was a linear association between maternal levels of B12 and preterm birth (per each 1-standard-deviation increase in B12, adjusted risk ratio = 0.89, 95% CI: 0.82, 0.97). Accordingly, B12 deficiency was associated with a higher risk of preterm birth (adjusted risk ratio = 1.21, 95% CI: 0.99, 1.49). This finding supports the need for randomized controlled trials of vitamin B12 supplementation in pregnancy.
authors.forename: Tormod
authors.initials: T
authors.lastname: Rogne
authors.forename: Myrte J
authors.initials: MJ
authors.lastname: Tielemans
authors.forename: Mary Foong-Fong
authors.initials: MF
authors.lastname: Chong
authors.forename: Chittaranjan S
authors.initials: CS
authors.lastname: Yajnik
authors.forename: Ghattu V
authors.initials: GV
authors.lastname: Krishnaveni
authors.forename: Lucilla
authors.initials: L
authors.lastname: Poston
authors.forename: Vincent W V
authors.initials: VW
authors.lastname: Jaddoe
authors.forename: Eric A P
authors.initials: EA
authors.lastname: Steegers
authors.forename: Suyog
authors.initials: S
authors.lastname: Joshi
authors.forename: Yap-Seng
authors.initials: YS
authors.lastname: Chong
authors.forename: Keith M
authors.initials: KM
authors.lastname: Godfrey
authors.forename: Fabian
authors.initials: F
authors.lastname: Yap
authors.forename: Raquel
authors.initials: R
authors.lastname: Yahyaoui
authors.forename: Tinku
authors.initials: T
authors.lastname: Thomas
authors.forename: Gry
authors.initials: G
authors.lastname: Hay
authors.forename: Marije
authors.initials: M
authors.lastname: Hogeveen
authors.forename: Ahmet
authors.initials: A
authors.lastname: Demir
authors.forename: Ponnusamy
authors.initials: P
authors.lastname: Saravanan
authors.forename: Eva
authors.initials: E
authors.lastname: Skovlund
authors.forename: Marit P
authors.initials: MP
authors.lastname: Martinussen
authors.forename: Geir W
authors.initials: GW
authors.lastname: Jacobsen
authors.forename: Oscar H
authors.initials: OH
authors.lastname: Franco
authors.forename: Michael B
authors.initials: MB
authors.lastname: Bracken
authors.forename: Kari R
authors.initials: KR
authors.lastname: Risnes
mesh_terms: D001724:Birth Weight; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D011247:Pregnancy / Q000097:blood*; D011248:Pregnancy Complications; D047928:Premature Birth / Q000209:etiology*; D012307:Risk Factors; D014805:Vitamin B 12 / Q000097:blood*; D014806:Vitamin B 12 Deficiency / Q000150:complications*
chemical_list: D014805:Vitamin B 12
keywords: low birth weight; pregnancy; preterm birth; systematic review; vitamin B12