IVF Assisted Hatching Study Shows No Benefit

This study will be of interest to couples that are being treated for infertility with

in vitro fertilization – IVF

. Specifically those who are having embryo transfer on day 3 and who are considering the technique known as assisted hatching.

The ability of an embryo to hatch, or escape, from the shell or zona pellucida that surrounds and protects the embryo during its first few days of development is one of many critical events that must occur for successful reproduction. Implantation of the embryo in the uterine lining is impossible unless hatching occurs. It has been suggested that impaired hatching of embryos resulting from IVF contributes to low implantation rates.

Assisted hatching or AZH has been proposed as a way of improving the chances for pregnancy in an IVF cycle. Assisted hatching has been used in two ways: creating a hole in the zona pellucida or simply thinning the zona. The techniques used for assisted hatching have varied from study to study. In the past, labs have used acid to dissolve the zona, mechanical disruption with sharp pipettes or lasers to vaporize the zona.

There has been considerable controversy over whether assisted hatching actually improves the chances for pregnancy. Some studies have shown a benefit, other studies have not. More than 15 years after the introduction of assisted hatching, its effectiveness and the indications for its use still remain poorly defined.

For example, a recent randomized study reported no benefit for assisted hatching among patients classified as poor prognosis because of either advanced age or elevated day 3 FSH levels.

Recently, a study was performed between 2001 and 2005 to evaluate the effects of assisted hatching with a laser on a specially selected IVF population that was thought to have a good prognosis. As such, there were several criteria for patients to be enrolled in this study. Females had to be under age 40 with a normal day 3 FSH level, and a normal uterus. During the IVF cycle, the plan was to be for a day 3 embryo transfer and the couples must have had good embryo quality. Patients were randomly assigned to receive laser-assisted hatching or no treatment.


A total of 203 patients were enrolled in the study. The average patient was 34 years old. An average 2.1 embryos were transferred into each patient. There was no difference in the pregnancy rate or miscarriage rate between the two groups.


This study was the first prospective randomized trial of large size to evaluate assisted hatching among selected patients with a good prognosis. The results indicate there is no benefit.

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