What is Assisted Hatching?
The early embryo consists of a ball of cells surrounded by a protective shell known as the zona pellucida. During later stages of development, the embryo has to break away from this outer coat by a process known as hatching. This assists the embryo to implant onto the lining of the uterus (womb).
Assisted Zona Hatching is a procedure which involves a hole being made in the shell of the developing embryo generated from IVF to aid the natural process of hatching. This is usually performed immediately prior to the embryo transfer procedure. There are several techniques used to make a hole in the shell of the embryo. The CRGH currently employs the laser zona drilling method.
Who Can Benefit from Assisted Hatching?
This technique might be advantageous for selected categories of patients, such as1-4:
- patients of advanced maternal age – this has been associated with hardening and thickening of the zona pellucida
- patients with repeated failed treatment cycles,
- patients with raised follicle stimulating hormone (FSH) and reduced ovarian reserve.
- Patients transferring frozen-thawed embryos – hardening of the zona pellucida has also been attributed to the freezing procedure.
Assisted hatching technique may therefore enhance pregnancy rates1-6. Whilst the use of assisted hatching is not evidence based, the clinic will only offer it when your consultant and/or embryologist deems it appropriate for the treatment.
What are the risks associated with Assisted Hatching?
During the early stages of embryo development, the outer shell (zona pellucida) serves as a protective barrier against foreign bodies. As assisted hatching involves breaching the outer shell, there are some extremely small risks associated with this procedure. These include:
- The developing embryo being exposed to harmful chemicals and micro-organisms,
- Further embryonic development may be affected, or the cells within the embryo may be expelled through the drilled hole and thereby causing the embryo to perish.
- The process of laser hatching has a very small risk of cell damage due to localised heat being applied to facilitate the opening in the zona pellucida.
- There is also an additional small risk (2%) that this procedure could entrap the embryo during the hatching process causing monozygotic twins (identical).
Assisted hatching is outlined as an additional treatment option by the Human Fertilisation and Embryology Authority (HFEA) and has currently been deemed as red in the HFEA traffic light system for additional treatment options as there is no evidence to show that it can improve live birth rates. Red-rated add-ons are considered by the HFEA experimental in nature. Please refer to the treatment add-ons page of the HFEA website7.
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- González-Ortega C, Cancino-Villarreall P, Anaya-Torres J, Pérez-Peña E, Gutierrez A. Impact of laser-assisted hatching (quarter technique) in poor prognosis patients. Ginecol Obstet Mex. 2015; 83 :670-9.
- Martins W, Rocha I, Ferriani R, Nastri C. Assisted hatching of human embryos: a systematic review and meta-analysis of randomized controlled trials. Human Reproduction Update. 2011; 17:438-53.
- Valojerdi, M.R., Eftekhari-Yazdi, P., Kariman L, Ashtiani S. Effect of laser zona pellucida opening on clinical outcome of assisted reproduction technology in patients with advanced female age, recurrent implantation failure, or frozen-thawed embryos. Fertil Steril 2008; 90 :84-91.
- Li, D., Yang, D., An, J, Jiao, J., Zhou, Y., Wu, Q., and Wang, X. Effect of assisted hatching on pregnancy outcomes: a systematic review and meta-analysis of randomized controlled trials. Sci Rep 2016; 6: 31228
- Fang C, Li T, Miao B, Zhuang G, Zhou C. Mechanically expanding the zona pellucida of human frozen thawed embryos: a new method of assisted hatching. Fert Steril 2010; 94:1302-1307.
- Cawood S, Doshi A, Gotts S, Serhal P (2010). Does assisted hatching improve the clinical outcome in vitrified-warmed embryo cycles? Reproductive BioMedicine Online 20 Suppl. 2 (2010) S47–S49. Abstract FC-4 Alpha 2010, 8th Biennial conference, Budapest, Hungary, 30th April-2nd May (FC-04)