title: Fetal/Placental weight ratio in term Japanese pregnancy: its difference among gender, parity, and infant growth.
abstract: OBJECTIVE
  The "inappropriately heavy placenta" has been considered to be associated with various pregnancy disorders; however, data is scarce what factors affect it. To determine whether the following three affect it; (1) infant gender and mother's parity, (2) growth restriction, and (3) preeclampsia.
  
  
  METHODS
  We employed fetal/placental weight ratio (F/P). Subjects consisted of 53,650 infants and their placentas from women who vaginally delivered singleton live term infants. First, we examined whether F/P differs among the infant's gender or mother's parity. We classified the population into 4 categories according to gender and parity: male, nulliparous (n=7,431), male, multiparous (n=7,859), female, nulliparous (n=7,559), female, multiparous (n=7,800), and, compared F/P among the four groups. Next, we determined whether F/P differs in "small" or "large" for gestational age (SGA or LGA) infants, compared with appropriate for gestational age infants. Last, we determined whether preeclampsia (representative disorder of SGA) affects F/P.
  
  
  RESULTS
  (1) F/P significantly differed according to infant gender and parity: female and nulliparity had significantly smaller F/P. F/P was significantly smaller in (2) SGA infants, and (3) infants from preeclamptic mothers.
  
  
  CONCLUSIONS
  We for the first time showed that in Japanese term vaginally-delivered singleton population, the following three had significantly smaller F/P than controls thus had "inappropriately heavy placenta": (1) female gender and nulliparity, (2) SGA infants, and (3) infants from preeclamptic mothers. We recommend that these factors should be taken into account in evaluating placental weight. These data may also be useful for further clarifying the fetal-placental pathophysiology in these conditions.
authors.affiliation: 1. Department of Obstetrics and Gynecology, Professor, International University of Health and Welfare Hospital, Professor, 537-3 Iguchi Nasushiobara, Tochigi 329-2763, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Matsuda
authors.affiliation: 2. Department of Obstetrics and Gynecology, Tokyo Women's Medical University, Associate professor, Kawada-cho, 8-1, Shinjuku-ku, Tokyo 162-8666, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Ogawa
authors.affiliation: 3. Department of Obstetrics and Gynecology, Tama-Nagayama Hospital, Nippon Medical School, Professor, 1-7-1 Nagayama, Tama-City, Tokyo 206-8512, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Nakai
authors.affiliation: 3. Department of Obstetrics and Gynecology, Tama-Nagayama Hospital, Nippon Medical School, Professor, 1-7-1 Nagayama, Tama-City, Tokyo 206-8512, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Hayashi
authors.affiliation: 4. Maternal and Perinatal Care Center, Oita Prefectural Hospital, Director, Bunyo 476, Oita 870-8511, Japan.
authors.forename: Shoji
authors.initials: S
authors.lastname: Satoh
authors.affiliation: 5. Department of Obstetrics and Gynecology, Jichi Medical University, Professor, 3311-1 Shimotsuke, Tochigi 329-0498, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Matsubara
mesh_terms: D044466:Asian People; D001724:Birth Weight; D015331:Cohort Studies; D005260:Female; D005317:Fetal Growth Retardation / Q000473:pathology; D005333:Fetus / Q000033:anatomy & histology*; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D007564:Japan; D008297:Male; D009929:Organ Size; D010298:Parity; D010920:Placenta / Q000033:anatomy & histology* / Q000473:pathology; D011225:Pre-Eclampsia / Q000473:pathology; D011247:Pregnancy; D012189:Retrospective Studies; D012727:Sex Characteristics
keywords: fetal/placental weight (F/P) ratio; placental weight; preeclampsia; small for gestational age