title: Decreasing full-term neonatal birthweight over the past 2 decades in a single institute in Japan.
abstract: OBJECTIVE
  The aim of this study was to investigate whether full-term neonatal birthweight is decreasing or not.
  
  
  METHODS
  Subjects were selected from the registration database of full-term singletons from a single local practitioner at two time-points, 1991 (n = 750) and 2011 (n = 442). Maternal age, parity, and smoking habits were recorded. Baseline characteristics included pre-pregnancy bodyweight (BW), body mass index (BMI), bodyweight before parturition, and weight gain during pregnancy. Neonatal birthweight and height were recorded. Variables correlated with neonatal size were investigated.
  
  
  RESULTS
  Male birthweight decreased from 3248 ± 409 (n = 373) to 3149 ± 430 g (n = 230) (P < 0.001). Female birthweight also decreased from 3148 ± 378 (n = 377) to 3063 ± 343 g (n = 212) (P < 0.01). Gestational age was shorter (40.1 ± 1.1 to 39.6 ± 1.1 weeks, P < 0.001). Pre-pregnancy maternal BMI did not change (20.7 ± 2.6, n = 750 to 20.5 ± 2.7, n = 442). Weight gain during pregnancy decreased (11.3 ± 3.8 to 10.8 ± 3.4 kg, P < 0.05) and was positively correlated with birthweight (P < 0.001). On multiple regression analysis, time was inversely correlated with birthweight, while it was positively correlated with pre-pregnancy BMI, weight gain during pregnancy, and gestational age.
  
  
  CONCLUSIONS
  In addition to maternal slenderness, increasing lower weight gain during pregnancy and medical intervention by physicians may in part contribute to the decrease in full-term birthweight over the past 2 decades.
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Kagoshima University, Kagoshima, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Orita
authors.forename: Masaki
authors.initials: M
authors.lastname: Tajima
authors.forename: Sayuri
authors.initials: S
authors.lastname: Hiwatashi
authors.forename: Sayori
authors.initials: S
authors.lastname: Terao
authors.forename: Ichiro
authors.initials: I
authors.lastname: Iwamoto
authors.forename: Toshimichi
authors.initials: T
authors.lastname: Oki
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Douchi
mesh_terms: D000293:Adolescent; D000328:Adult; D001724:Birth Weight; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007564:Japan; D008297:Male; D011247:Pregnancy; D012044:Regression Analysis; D013997:Time Factors; D055815:Young Adult