title: Associations of maternal pre-pregnancy underweight with small-for-gestational-age and spontaneous preterm birth, and optimal gestational weight gain in Japanese women.
abstract: OBJECTIVE
  To determine associations of maternal pre-pregnancy underweight with poor outcomes and evaluate how gestational weight gain affects risks for such outcomes in pre-pregnancy underweight Japanese women.
  
  
  METHODS
  By analyzing the January 2001-December 2012 hospital database, we retrospectively identified 6954 women with pre-pregnancy normal weights (body mass index, 18.5-24.9 kg/m²) and 1057 pre-pregnancy underweight women (body mass index, <18.5 kg/m²) who delivered at the Perinatal Maternity and Neonatal Center of Yokohama City University. These women were stratified by weekly weight gain during the second/third trimesters to investigate associations of gestational weight gain with spontaneous preterm birth and small for gestational age (SGA). Spontaneous preterm birth and SGA incidences were compared with those of women meeting Institute of Medicine (IO M) guidelines to determine optimal weight gain in Japanese women.
  
  
  RESULTS
  Preterm birth and SGA incidences were significantly higher in pre-pregnancy underweight than in pre-pregnancy normal weight women (4.6% vs 2.4% [P=0.005] and 13.9% vs 9.7% [P = 0.003], respectively). For pre-pregnancy normal weight women, preterm birth incidence was significantly higher in those with weight gain of less than 0.2 kg/week than in those IOM guidelines. For pre-pregnancy underweight women, preterm birth and SGA incidences were significantly higher in those with weight gain of less than 0.3 kg/week than in those meeting IOM guidelines.
  
  
  CONCLUSIONS
  Preterm birth and SGA incidences did not differ significantly between pre-pregnancy normal weight women with weight gain of 0.2 kg/week or more and pre-pregnancy underweight women with weight gain of 0.3 kg/week or more, as compared to women meeting IOM guidelines. These results suggest that IOM guidelines for gestational weight gain may lack external validity in Japanese women.
authors.affiliation: Perinatal Center for Maternity and Neonatal, Yokohama City University Medical Center, Yokohama, Japan.
authors.forename: Kana
authors.initials: K
authors.lastname: Fujiwara
authors.forename: Shigeru
authors.initials: S
authors.lastname: Aoki
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kurasawa
authors.forename: Mika
authors.initials: M
authors.lastname: Okuda
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Takahashi
authors.forename: Fumiki
authors.initials: F
authors.lastname: Hirahara
mesh_terms: D000046:Academic Medical Centers; D000328:Adult; D015992:Body Mass Index; D005260:Female; D005317:Fetal Growth Retardation / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology*; D006293:Health Promotion; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D007564:Japan / Q000453:epidemiology; D008297:Male; D039382:Maternal Nutritional Physiological Phenomena / Q000208:ethnology; D018673:Nutrition Policy; D010349:Patient Compliance / Q000208:ethnology; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology*; D012189:Retrospective Studies; D012307:Risk Factors; D013851:Thinness / Q000208:ethnology / Q000503:physiopathology*; D015430:Weight Gain / Q000208:ethnology
keywords: Japanese women; body mass index; gestational weight gain; preterm birth; small for gestational age