title: The effect of single embryo transfer on perinatal outcomes in Japan.
abstract: OBJECTIVE
  In 2007 and 2008, the Japan Society for Reproductive Medicine and the Japan Society of Obstetrics and Gynecology issued a recommendation for single embryo transfer (SET). Thereafter, SET was implemented in 73% of in vitro fertilization (IVF) cases in Japan. The purpose of this study was to evaluate the effects of compliance with the SET recommendation on perinatal outcomes.
  
  
  METHODS
  An electronic audit of the perinatal database of the Japanese Society of Obstetrics and Gynecology was conducted from 2001 through 2010. The database comprised data of 610,726 women. Totally, 20,923 women conceived through IVF. To compare perinatal outcomes, these women were categorized into two study groups depending on whether they conceived before (2004-2005, n=3,865) or after (2009-2010, n=6,842) the SET recommendation statement was issued.
  
  
  RESULTS
  The proportion of women who conceived through IVF increased from 1.3% in 2001 to 4.8% in 2010. Compliance with the SET recommendation led to a decrease in the incidence of twin pregnancies (33.9% versus 13%, p<0.01), incidence of preterm delivery (odds ratio [OR]: 0.54, 95% confidence interval [CI]: 0.50-0.59), low birth weight (OR: 0.42, 95% CI: 0.39-0.45), and neonatal intensive care unit admission (OR 0.70, 95% CI 0.65-0.76), but an increase in the incidence of monochorionic twins (1.6% versus 2.5%, p<0.01).
  
  
  CONCLUSIONS
  Compliance with the SET recommendation improved perinatal outcomes by reducing the incidence of twin pregnancies.
authors.affiliation: 1. Department of Obstetrics and Gynecology, Nippon Medical School, Tokyo, Japan;
authors.forename: Masako
authors.initials: M
authors.lastname: Hayashi
authors.affiliation: 2. Maternal and Perinatal Care Center, Oita Prefectural Hospital, Oita, Japan;
authors.forename: Shoji
authors.initials: S
authors.lastname: Satoh
authors.affiliation: 3. Department of Obstetrics and Gynecology, International University of Health and Welfare, Tochigi, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Matsuda
authors.affiliation: 1. Department of Obstetrics and Gynecology, Nippon Medical School, Tokyo, Japan;
authors.forename: Akihito
authors.initials: A
authors.lastname: Nakai
mesh_terms: D000328:Adult; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods* / Q000706:statistics & numerical data; D019983:Guideline Adherence; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007564:Japan / Q000453:epidemiology; D008423:Maternal Age; D008875:Middle Aged; D011247:Pregnancy; D011256:Pregnancy Outcome; D047928:Premature Birth / Q000453:epidemiology / Q000209:etiology; D056826:Single Embryo Transfer / Q000379:methods* / Q000706:statistics & numerical data; D014427:Twins / Q000706:statistics & numerical data; D055815:Young Adult
keywords: in vitro fertilization; monochorionic twin; obstetric outcome; perinatal outcome.; twin pregnancy