title: How Many Embryos should be Transferred? The Relevance of Parity and Obstetric History.
abstract: BACKGROUND
  Fertility treatments are responsible for the rise in high order pregnancies in recent decades and their associated complications. Reducing the number of embryos returned to the uterus will reduce the rate of high order pregnancies.
  
  
  OBJECTIVE
  To explore whether obstetric history and parity have a role in the clinician's decision making regarding the number of embryos transferred to the uterus during in vitro fertilization (IVF).
  
  
  METHODS
  In a retrospective study for the period August 2005 to March 2012, data of twin deliveries > 24 weeks were collected, including parity, mode of conception (IVF vs. spontaneous), gestational age at delivery, preeclampsia, birth weight, admission to the neonatal intensive care unit (NICU), and Apgar scores.
  
  
  RESULTS
  A total of 1651 twin deliveries > 24 weeks were record- ed, of which 959 (58%) were at term (> 37 weeks). The early preterm delivery (PTD) rate (< 32 weeks) was significantly lower with increased parity (12.6%, 8.5%, and 5.6%, in women with 0, 1, and ≥ 2 previous term deliveries, respectively). Risks for PTD (< 37 weeks), preeclampsia and NICU admission were significantly higher in primiparous women compared to those who had one or more previous term deliveries. Primiparity and preeclampsia, but not IVF, were significant risk factors for PTD.
  
  
  CONCLUSIONS
  The risk for PTD in twin pregnancies is significantly lower in women who had a previous term delivery and decreases further after two or more previous term deliveries. This finding should be considered when deciding on the number of embryos to be transferred in IV.
authors.forename: Doron
authors.initials: D
authors.lastname: Goldberg
authors.forename: Avi
authors.initials: A
authors.lastname: Tsafrir
authors.forename: Naama
authors.initials: N
authors.lastname: Srebnik
authors.forename: Michael
authors.initials: M
authors.lastname: Gal
authors.forename: Ehud J
authors.initials: EJ
authors.lastname: Margalioth
authors.forename: Pnina
authors.initials: P
authors.lastname: Mor
authors.forename: Rivka
authors.initials: R
authors.lastname: Farkash
authors.forename: Arnon
authors.initials: A
authors.lastname: Samueloff
authors.forename: Talia
authors.initials: T
authors.lastname: Eldar-Geva
mesh_terms: D000328:Adult; D001034:Apgar Score; D036861:Delivery, Obstetric / Q000706:statistics & numerical data; D004624:Embryo Transfer / Q000009:adverse effects / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects / Q000379:methods / Q000706:statistics & numerical data; D005865:Gestational Age; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007557:Israel / Q000453:epidemiology; D010298:Parity; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology; D059285:Pregnancy, Twin / Q000706:statistics & numerical data; D047928:Premature Birth / Q000453:epidemiology / Q000209:etiology; D017584:Reproductive History; D012189:Retrospective Studies