Assisted hatching, a micromanipulation technique that facilitates the embryo hatching process through the thinning or breaching of the zona pellucida (ZP), has been reported to increase the success rates of IVF. Now, a randomized, double-blinded trial reports that the procedure does not improve implantation, clinical pregnancy, or live birth rates during IVF in women younger than 38 years with embryos having ZP thickness of ≥13μm. The findings of the study have been published in the recent issue of the journal, Fertility and Sterility.
The study headed by Randall Odem, Professor of Obstetrics and Gynecology, Washington University School of Medicine, Missouri, determined the effects of assisted hatching in subjects aged <38 years, having embryos with a thickened ZP. The prospective crossover study involved 121 women, who underwent egg retrieval and IVF procedure during the period April 2004 to February 2007 at the university. Patients’ embryos were evaluated on the third day following fertilization, and ZP thickness measured. The eligible participants, who had embryos with ZP >12μm, were randomized into 2 groups: unhatched (no procedure) and hatched (performed by acidic Tyrode’s solution). The outcomes measured included clinical intrauterine pregnancy rate, implantation rate, spontaneous pregnancy loss and live birth rate.
The study results did not show any substantial difference in clinical pregnancy (hatched=47% vs. unhatched=50%) or live birth (hatched=46% vs. unhatched= 45%) rates between the two groups. Similar findings were observed in the two groups with respect to the rates of ectopic gestations, spontaneous abortions, monozygotic or dizygotic twinning, or chromosomal abnormalities. Also, the researchers noted that pregnancy was not significantly affected by the mean ZP thickness. Based on the findings, the scientists concluded that assisted hatching may not be beneficial to IVF patients <38 years.
Earlier, Ali, et al. (Journal of Assisted Reproduction and Genetics, 2003) validated their previous study findings that assisted hatching is effective only in young patients. Laser assisted hatching (LAH) was performed on 2 out of the 3 embryos before the transfer. Controls had similar characteristics and protocol except that they were not subjected to LAH.
The researchers found that the clinical pregnancy rate was 64.9% in women ≤36 years, whose embryos were treated with LAH, while it was 33.3% in controls. Similarly, the women in the test group had a higher implantation rate than those whose embryos were not subjected to LAH (38.1% vs. 17.5%). Results indicated that the benefits of LAH can be observed in:
• subjects aged ≤36 but not in those ≥37 years
• embryos with thin ZP, i.e., ≤16μm but not in ZP of ≥17μm
• women with repeated failures (37-50%).
The Practice Committee of the Society for Assisted Reproductive Technology (SART) and American Society for Reproductive Medicine (ASRM) reported that there is lack of substantial evidence to support the use of assisted hatching in all IVF cycles. However, it is clinically beneficial in subjects with poor prognosis, such as those with previous history of ≥2 IVF failures, poor quality embryos, and women aged ≥38 years.
References
1. Assisted hatching during IVF does not improve pregnancy rates in women younger than 38. News Release. Washington University in St. Louis. Last Accessed April 20, 2009.
2. Hagemann AR, Lanzendorf SE, Jungheim ES, Chang AS, Ratts VS, Odem RR. A prospective, randomized, double-blinded study of assisted hatching in women younger than 38 years undergoing in vitro fertilization. Fertil Steril. 2009 Mar 5. [Epub ahead of print]
3. Ali J, Rahbar S, Burjaq H, Sultan AM, Al Flamerzi M, Shahata MA. Routine laser assisted hatching results in significantly increased clincal pregnancies. J Assist Reprod Genet. 2003 May;20(5):177-81.
