title: Standard curves of placental weight and fetal/placental weight ratio in Japanese population: difference according to the delivery mode, fetal sex, or maternal parity.
abstract: OBJECTIVE
  Placental weight (PW) and fetal/placental weight ratio (F/P) have been considered to be useful parameters for understanding the pathophysiology of fetal growth. However, there have been no standard data on PW and F/P in Asian populations. This study was conducted to establish nomograms of PW and F/P in the Japanese population and to clarify characteristics of PW and F/P in this population.
  
  
  METHODS
  Included in the study were 79,590 Japanese cases: 58,871 vaginal and 20,719 cesarean deliveries at obstetrical facilities (2001-2002) and registered to the Japan Society of Obstetrics and Gynecology Database. Multiple pregnancies, stillbirths, and fetal anomalies were excluded. Nomograms of PW and F/P were created by spline methods in groups categorized by fetal sex (male or female) and maternal parity (primipara or multipara).
  
  
  RESULTS
  Standard curves of PW and F/P were established, which indicated that PW and F/P were lower in cesarean deliveries than vaginal deliveries, especially during preterm period. PW differed depending on fetal sex and maternal parity. F/P differed according to fetal sex.
  
  
  CONCLUSIONS
  We for the first time established standard curves of PW and F/P in the Japanese population with statistically sufficient data, which showed that PW and F/P were lower in cesarean deliveries. PW and F/P were also affected by fetal sex. These data might be useful to understand the pathophysiology between the fetus and placenta in utero.
authors.affiliation: Perinatal Medical Center, Tokyo Women's Medical University, Kawadacho 8-1, Shinjuku, Tokyo 1628666, Japan. Electronic address: masakiogawa3@gmail.com.
authors.forename: Masaki
authors.initials: M
authors.lastname: Ogawa
authors.affiliation: Department of Obstetrics and Gynecology, International University of Health and Welfare Hospital, 537-3 Iguchi Nasushiobara, Tochigi 3292763, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Matsuda
authors.affiliation: Department of Obstetrics and Gynecology, Tama-Nagayama Hospital, Nippon Medical School, 1-7-1 Nagayama, Tama City, Tokyo 2068512, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Nakai
authors.affiliation: Department of Obstetrics and Gynecology, Tama-Nagayama Hospital, Nippon Medical School, 1-7-1 Nagayama, Tama City, Tokyo 2068512, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Hayashi
authors.affiliation: Maternal and Perinatal Care Center, Oita Prefectural Hospital Bunyo 476, Oita 8708511, Japan.
authors.forename: Shoji
authors.initials: S
authors.lastname: Sato
authors.affiliation: Department of Obstetrics and Gynecology, Jichi Medical University, 3311-1 Shimotsuke, Tochigi 3290498, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Matsubara
mesh_terms: D001724:Birth Weight / Q000502:physiology*; D036861:Delivery, Obstetric / Q000379:methods*; D005260:Female; D020567:Fetal Weight / Q000502:physiology*; D006801:Humans; D007231:Infant, Newborn; D007564:Japan; D008297:Male; D049451:Nomograms; D009929:Organ Size / Q000502:physiology; D010298:Parity / Q000502:physiology*; D010920:Placenta / Q000033:anatomy & histology*; D011247:Pregnancy; D012016:Reference Values
keywords: Birth weight; Fetal/placental weight ratio; Placental weight; Standard curve