Embryo culture

Embryo culture is a component of in vitro fertilisation where in resultant embryos are allowed to grow for some time in an artificial medium .

Duration

Further information: Embryo transfer

The duration of embryo culture can be varied, conferring different stages of embryogenesis at embryo transfer. The main stages at which embryo transfer is performed are cleavage stage (day 2 to 4 after co-incubation) or the blastocyst stage (day 5 or 6 after co-incubation).[1]

Embryos which reach the day 3 cell stage can be tested for chromosomal or specific genetic defects prior to possible transfer by preimplantation genetic diagnosis (PGD). Embryo culture until the blastocyst stage confers a significant increase in live birth rate per embryo transfer, but also confers a decreased number of embryos available for transfer and embryo cryopreservation, so the cumulative clinical pregnancy rates are increased with cleavage stage transfer.[2] Transfer day 2 instead of day 3 after fertilization has no differences in live birth rate.[2]

Monozygotic twinning is not increased after blastocyst transfer compared with cleavage-stage embryo transfer.[3]

There are significantly higher odds of preterm birth (odds ratio 1.3) and congenital anomalies (odds ratio 1.3) among births from embryos cultured until the blastocyst stage compared with cleavage stage.[1]

Techniques

Culture of embryos can either be performed in an artificial culture medium or in an autologous endometrial coculture (on top of a layer of cells from the woman's own uterine lining). With artificial culture medium, there can either be the same culture medium throughout the period, or a sequential system can be used, in which the embryo is sequentially placed in different media. For example, when culturing to the blastocyst stage, one medium may be used for culture to day 3, and a second medium is used for culture thereafter.[4] Single or sequential medium are equally effective for the culture of human embryos to the blastocyst stage.[5] Artificial embryo culture media basically contain glucose, pyruvate, and energy-providing components, but the addition of amino acids, nucleotides, vitamins, and cholesterol improve the performance of embryonic growth and development.[6] Methods to permit dynamic embryo culture with fluid flow and embryo movement are also available.[7] A new method in development uses the uterus as an incubator and the naturally occurring intrauterine fluids as culture medium by encapsulating the embryos in a permeable intrauterine vessel.[8]

A review in 2013 meta-analysis of commercially available IVF culture media was unable to identify a specific media that was superior in terms of pregnancy outcome.[9]

Usage of low oxygen concentrations of 5% rather than about 20% in the atmosphere has been shown to increase live birth rate to a relative probability of 1.24, without any evidence of increased risk for multiple pregnancies, miscarriages or congenital abnormalities.[10]

Risks

Animal studies have detected epigenetic abnormalities in embryos having undergone embryo culture, indicating a need to optimize the procedures.[11]

References

  1. 1 2 Dar, S.; Lazer, T.; Shah, P. S.; Librach, C. L. (2014). "Neonatal outcomes among singleton births after blastocyst versus cleavage stage embryo transfer: a systematic review and meta-analysis". Human Reproduction Update 20 (3): 439–448. doi:10.1093/humupd/dmu001. ISSN 1355-4786. PMID 24480786.
  2. 1 2 Farquhar, Cindy; Rishworth, Josephine R; Brown, Julie; Nelen, Willianne LDM; Marjoribanks, Jane; Brown, Julie (2013). "Assisted reproductive technology: an overview of Cochrane Reviews". Cochrane Database Syst Rev 8: CD010537. doi:10.1002/14651858.CD010537.pub2. PMID 23970457.
  3. ↑ Papanikolaou EG, Fatemi H, Venetis C; et al. (February 2009). "Monozygotic twinning is not increased after single blastocyst transfer compared with single cleavage-stage embryo transfer". Fertil. Steril. 93 (2): 592–7. doi:10.1016/j.fertnstert.2008.12.088. PMID 19243755.
  4. ↑ Comparison Of A Single Medium With Sequential Media For Development Of Human Embryos To The Blastocyst Stage Melanie R. Freeman and Don Rieger. Nashville Fertility Center, Nashville, TN, U.S.A. and LifeGlobal, Guelph, ON, Canada
  5. ↑ Single or sequential medium are equally effective for the culture of human embryos to the blastocyst stage: a pilot study D.T. Schneidera, S. Verza Jr.a and S.C. Estevesa" Fertility and Sterility, Volume 92, Issue 3, Supplement 1, September 2009, Pages S231-S232
  6. ↑ Xella S, Marsella T, Tagliasacchi D, et al. (April 2010). "Embryo quality and implantation rate in two different culture media: ISM1 versus Universal IVF Medium". Fertil. Steril. 93 (6): 1859–63. doi:10.1016/j.fertnstert.2008.12.030. PMID 19152877.
  7. ↑ Swain JE, Smith GD (2011). "Advances in embryo culture platforms: novel approaches to improve preimplantation embryo development through modifications of the microenvironment". Hum. Reprod. Update 17 (4): 541–57. doi:10.1093/humupd/dmr006. PMID 21454356.
  8. ↑ Blockeel, C.; Mock, P.; Verheyen, G.; Bouche, N.; Le Goff, P.; Heyman, Y.; Wrenzycki, C.; Höffmann, K.; Niemann, H.; Haentjens, P.; De Los Santos, M. J.; Fernandez-Sanchez, M.; Velasco, M.; Aebischer, P.; Devroey, P.; Simón, C. (2008). "An in vivo culture system for human embryos using an encapsulation technology: A pilot study". Human Reproduction 24 (4): 790–796. doi:10.1093/humrep/dep005. PMC 2656929. PMID 19273881.
  9. ↑ Mantikou, E.; Youssef, M. A. F. M.; Van Wely, M.; Van Der Veen, F.; Al-Inany, H. G.; Repping, S.; Mastenbroek, S. (2013). "Embryo culture media and IVF/ICSI success rates: A systematic review". Human Reproduction Update 19 (3): 210–220. doi:10.1093/humupd/dms061. PMID 23385469.
  10. ↑ Mantikou, E.; Bontekoe, S.; Van Wely, M.; Seshadri, S.; Repping, S.; Mastenbroek, S. (2013). "Low oxygen concentrations for embryo culture in assisted reproductive technologies". Human Reproduction Update 19 (3): 209. doi:10.1093/humupd/dms055. PMID 23377864.
  11. ↑ Anckaert, E.; De Rycke, M.; Smitz, J. (2012). "Culture of oocytes and risk of imprinting defects". Human Reproduction Update 19 (1): 52–66. doi:10.1093/humupd/dms042. PMID 23054129.
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