title: Blastocyst culture using single versus sequential media in clinical IVF: a systematic review and meta-analysis of randomized controlled trials.
abstract: OBJECTIVE
  The purpose of this study was to undertake a review of the available evidence comparing the use of a single medium versus sequential media for embryo culture to the blastocyst stage in clinical IVF.
  
  
  METHODS
  We searched the Cochrane Central, PubMed, Scopus, ClinicalTrials.gov, Current Controlled Trials and WHO International Clinical Trials Registry Platform to identify randomized controlled trials comparing single versus sequential media for blastocyst culture and ongoing pregnancy rate. Included studies randomized either oocytes/zygotes or women. Eligible oocyte/zygote studies were analyzed to assess the risk difference (RD) and 95 % confidence intervals (CI) between the two media systems; eligible woman-based studies were analyzed to assess the risk ratio (RR) and 95 % CI for clinical pregnancy rate.
  
  
  RESULTS
  No differences were observed between single and sequential media for either ongoing pregnancy per randomized woman (relative risk (RR) = 0.9, 95 % CI = 0.7 to 1.3, two studies including 246 women, I2= 0 %) or clinical pregnancy per randomized woman (RR = 1.0, 95 % CI = 0.7 to 1.4, one study including 100 women); or miscarriage per clinical pregnancy: RR = 1.3, 95 % CI = 0.4 to 4.3, two studies including 246 participants, I2= 0 %). Single media use was associated with an increase blastocyst formation per randomized oocyte/zygote (relative distribution (RD) = +0.06, 95 % CI = +0.01 to +0.12, ten studies including 7455 oocytes/zygotes, I2= 83 %) but not top/high blastocyst formation (RD = +0.05, 95 % CI = -0.01 to +0.11, five studies including 3879 oocytes/zygotes, I2= 93 %). The overall quality of the evidence was very low for all these four outcomes.
  
  
  CONCLUSIONS
  Although using a single medium for extended culture has some practical advantages and blastocyst formation rates appear to be higher, there is insufficient evidence to recommend either sequential or single-step media as being superior for the culture of embryos to days 5/6. Future studies comparing these two media systems in well-designed trials should be performed.
authors: Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, UK.|Eugonia Assisted Reproduction Unit, Athens, Greece.
authors: Ioannis A
authors: IA
authors: Sfontouris
authors: Department of Obstetrics and Gynecology, Ribeirao Preto Medical School, University of Sao Paulo, Ribeirao Preto, Brazil.
authors: Wellington P
authors: WP
authors: Martins
authors: Department of Obstetrics and Gynecology, Ribeirao Preto Medical School, University of Sao Paulo, Ribeirao Preto, Brazil.|SEMEAR fertilidade, Reproductive Medicine, Ribeirao Preto, Brazil.
authors: Carolina O
authors: CO
authors: Nastri
authors: Department of Obstetrics and Gynecology, Ribeirao Preto Medical School, University of Sao Paulo, Ribeirao Preto, Brazil.|SEMEAR fertilidade, Reproductive Medicine, Ribeirao Preto, Brazil.
authors: Iara G R
authors: IG
authors: Viana
authors: Department of Obstetrics and Gynecology, Ribeirao Preto Medical School, University of Sao Paulo, Ribeirao Preto, Brazil.
authors: Paula A
authors: PA
authors: Navarro
authors: Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, UK.
authors: Nick
authors: N
authors: Raine-Fenning
authors: HRP (the UNDP/UNFPA/UNICEF/WHO/World Bank Special Programme of Research, Development and Research Training in Human Reproduction), Geneva, Switzerland.|Population Council, Reproductive Health Programme, New York, USA.
authors: Sheryl
authors: S
authors: van der Poel
authors: GENERA Centre for Reproductive Medicine, Clinica Valle Giulia, via de Notaris 2b, Rome, Italy.
authors: Laura
authors: L
authors: Rienzi
authors: Department of Obstetrics, Gynecology and Reproductive Biology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, 02115, MA, USA. cracowsky@partners.org.
authors: Catherine
authors: http://orcid.org/0000-0002-8961-7896
authors: C
authors: Racowsky
mesh_terms: D000328:Adult; D001755:Blastocyst; D002970:Cleavage Stage, Ovum; D046149:Embryo Culture Techniques / Q000379:methods*; D004624:Embryo Transfer / Q000379:methods*; D047108:Embryonic Development; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods; D006801:Humans; D050498:Live Birth; D009865:Oocytes / Q000254:growth & development*; D011247:Pregnancy; D018873:Pregnancy Rate; D016032:Randomized Controlled Trials as Topic
keywords: Blastocyst; Culture; Extended; Medium; Sequential; Single