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Assisted Hatching

Embryos which are ready for transfer on Day 2 or 3 of development can undergo an additional procedure called Assisted Hatching (AH). The literature suggests that by using AH on embryos there may be an improvement in implantation on day 6 or 7 of development. AH is also part of the Preimplantation Genetic Screening (PGS) process, as it is necessary to create a hole in the embryo in order to remove a cell from the embryo for genetic screening.

Women who may benefit most from AH

  • Women using their own eggs who are older than 38.
  • Women who have had a history of failed IVF attempts using their own eggs.
  • Women who have had a poor response to medication for an IVF cycle and only have 1 or two embryos for transfer.
  • Women who are using embryos in a freeze / thaw cycle (FET).


When an embryo undergoes AH a hole is made in the zona pellucida or shell of the developing embryo. This can be accomplished by using a weak acid or laser.


The Acid Method

When AH is performed using a weak acid, the liquid is gently blown over a specific site on the surface of the embryo’s shell. The acid will flow and fan out over the shell as the hole is made. This may expose the embryo to too much of the acid. The acid method may cause a larger opening that intended causing cells to be damaged or fall out of the shell.





The Laser Method

When AH is performed using a laser it does not have to be removed from its culture dish and placed in a separate “hatching plate”. The laser is attached directly to the microscope as an objective. The embryo is positioned for AH and the laser is applied 2 or 3 times until a hole is made through the shell. There is no exposure to chemicals and the time the embryo spends outside the incubator is significantly less than when AH is performed using the Acid-Method.



We have provided the following article for your information regarding Assisted Hatching.

The role of assisted hatching in in-vitro fertilization: a review of the literature. A Committee opinion The Practice Committee of the Society for Assisted Reproductive Technologya and the Practice Committee of the American Society for Reproductive Medicine b

a Society for Assisted Reproductive Technology and b American Society for Reproductive Medicine, Birmingham, Alabama.

Hatching of the blastocyst is a critical step in the sequence of physiologic events culminating in implantation. Failure to hatch [due to intrinsic abnormalities in either the blastocyst or zona pellucida (ZP)] may be one of many factors limiting human reproductive efficiency. Assisted hatching involves the artificial thinning or breaching of the ZP and has been proposed as one technique to improve implantation and pregnancy rates following in vitro fertilization (IVF). An increased implantation rate following mechanical opening of the ZP (partial zona dissection-PZD) was first reported in 1990 (1). A randomized, prospective trial of selected assisted hatching 72 hours post-retrieval (zona drilling with acidified Tyrode’s solution) suggested an improvement in implantation rates when the procedure was selectively applied to embryos with a “poor prognosis” (based on zona thickness, blastomere number, fragmentation rates, maternal age, etc.)(2). Since these early reports, many assisted reproductive technology (ART) programs have incorporated the use of assisted hatching in efforts to improve clinical outcomes. The assisted hatching procedure is generally performed on day 3 after fertilization using various methods. These include the creation of an opening in the zona either by drilling with acidified Tyrode’s solution (3, 4), PZD with a glass microneedle (5), laser photoablation (6), or use of a piezo-micromanipulator (7). The ZP can be artificially thinned without breaching its integrity with proteolytic enzymes, acidified Tyrode’s solution, or laser (8, 9). The assisted hatching procedure may be associated with specific complications independent of the IVF procedure itself, including lethal damage to the embryo and damage to individual blastomeres with reduction of embryo viability. In addition, artificial manipulation of the ZP has been associated with an increased risk of monozygotic twinning (10, 11). Patients whose embryos are hatched are often treated with antibiotics and steroids before and after embryo transfer, exposing them to the potential risks and side effects of such treatments. Success rates following the use of assisted hatching in different ART programs have varied considerably. However, differences in patient populations, operator experience, hatching technique, and study design make it difficult to compare directly reports from different centers. A comprehensive review and meta-analysis (12, 13) identified 23 randomized controlled trials involving 2,572 women undergoing assisted hatching during ART. Seven studies were identified in abstract form only and had not appeared in the peer-reviewed literature at the time of the review. Clinical pregnancy rates were evaluated in 19 trials (722 clinical pregnancies, 2,175 women) and demonstrated an improvement following assisted hatching (OR 1.63; 95% CI 1.27–2.09), but with significant heterogeneity. Subgroups of patients who demonstrated the greatest improvement in clinical pregnancy rates were those with prior failed ART cycles (OR 2.33; 95% CI 1.63–3.34) and older women. Only six of the studies included in the analysis (involving 523 women) reported live birth rates with and without assisted hatching (Table 1). Overall, live birth rates in the two groups were not different, although the various study populations were heterogeneous (OR 1.26; 95% CI 0.82–1.78). Assuming a delivery rate of 30% in the control group overall, a total of 720 patients would be required to detect a 10% difference in delivery rates between the two groups (P_.05). The numbers of live births reported in studies thus far therefore do not allow a confident conclusion regarding the clinical efficacy of assisted hatching procedures. Three studies (8, 9, 14) have evaluated the effects of different methods of assisted hatching, including acidified Tyrode’s solution, thinning with proteolytic enzymes, mechanical dissection, and laser energy. Results have varied and likely reflect, at least in part, variations in the level of experience and hatching methods.

The available published evidence does not support the routine or universal application of assisted hatching in all IVF cycles at this time. Assisted hatching may be clinically useful in patients with a poor prognosis, including those with 2 failed IVF cycles and poor embryo quality and older women (38 years of age) (15). Higher clinical pregnancy and implantation rates have been observed after assisted hatching. However, delivery rates have not significantly improved, possibly because the small sample sizes in studies reporting delivery rates have lacked sufficient power to detect a difference. Individual ART programs should evaluate their own unique patient populations to determine which subgroup(s) of patients, if any, may benefit from assisted hatching.
Committee Opinion
Reviewed June 2006.

Received October 21, 2005; revised and accepted December 2, 2005.
Reprints will not be available.
S124 Fertility and Sterility_ Vol. 86, Suppl 4, November 2006 0015-0282/06/$32.00
Copyright ©2006 American Society for Reproductive Medicine,
Published by Elsevier Inc. doi: 10.1016/j.fertnstert.2006.09.001


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