title: Effects of maternal factors on birth weight in Japan.
abstract: OBJECTIVE
  We investigated the possible factors related to the birth weight (BW) using the Japanese perinatal database.
  
  
  METHODS
  The live infants born at 37 to 41 weeks of gestation were enrolled in this study. Cases with diabetic pregnancy, preeclampsia, an anomalous fetus, and a fetus with chromosomal abnormalities were excluded. A multiple regression analysis for confounding factors and an analysis of covariance (ANCOVA) for comparing the BW in 2006 and 2010 were used for the statistical analysis.
  
  
  RESULTS
  The BW significantly decreased from 2950.8 g in 2006 (n = 27,723) to 2937.5 g in 2010 (n = 38,008) in the overall population, and this decrease was similar for male and female neonates. All confounding factors, except for the mode of delivery, affected the BW. Primiparity, smoking, and a female gender were related to the decrease in BW, whereas maternal age, maternal height, weight gain during pregnancy, BMI, the use of in vitro fertilization, induction of labor, and gestational duration were related to an increased BW. The ANCOVA showed that no significant change of the BW was seen between 2006 and 2010 (the difference was 2.164 g, P = 0.414).
  
  
  CONCLUSIONS
  The gestational duration is the most important factor affecting the BW in singleton term infants.
authors.affiliation: Department of Obstetrics and Gynecology, Tokyo Women's Medical University, Kawada-cho 8-1, Shinjuku-ku, Tokyo 162-8666, Japan.
authors.forename: Misato
authors.initials: M
authors.lastname: Terada
authors.affiliation: Department of Obstetrics and Gynecology, Tokyo Women's Medical University, Kawada-cho 8-1, Shinjuku-ku, Tokyo 162-8666, Japan ; Department of Obstetrics and Gynecology, International University of Health and Welfare Hospital, 537-3 Iguchi Nasushiobara, Tochigi 329-2763, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Matsuda
authors.affiliation: Department of Obstetrics and Gynecology, Tokyo Women's Medical University, Kawada-cho 8-1, Shinjuku-ku, Tokyo 162-8666, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Ogawa
authors.affiliation: Department of Obstetrics and Gynecology, Tokyo Women's Medical University, Kawada-cho 8-1, Shinjuku-ku, Tokyo 162-8666, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Matsui
authors.affiliation: Maternal and Perinatal Care Center, Oita Prefectural Hospital, Bunyo 476, Oita 870-8511, Japan.
authors.forename: Shoji
authors.initials: S
authors.lastname: Satoh
mesh_terms: D001724:Birth Weight; D002585:Cesarean Section / Q000706:statistics & numerical data; D015986:Confounding Factors, Epidemiologic; D036861:Delivery, Obstetric / Q000706:statistics & numerical data; D005260:Female; D005307:Fertilization in Vitro / Q000706:statistics & numerical data; D005320:Fetal Macrosomia / Q000453:epidemiology; D005865:Gestational Age; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007564:Japan / Q000453:epidemiology; D007751:Labor, Induced / Q000706:statistics & numerical data; D008297:Male; D008423:Maternal Age; D015999:Multivariate Analysis; D010298:Parity; D011247:Pregnancy; D012044:Regression Analysis; D012189:Retrospective Studies; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology; D015430:Weight Gain