The assisted hatching procedure, like ICSI, is carried out by a technique known as micromanipulation. In small dishes the embryos, which now contain an average of six to eight cells, are stabilized by a holding pipette, while on the opposite side a small pipette containing acidified Tyrode’s solution creates a small defect in the zona. The size of the defect is critical; if it is too small it may pinch off the embryo during hatching and either reduce the chance of implantation or cause identical twinning. The embryos are then rinsed to remove any excess acid solution and returned to the incubator for a few hours before transfer into the uterus.
This relatively small variation in the IVF procedure has yielded dramatic results. Since all micromanipulation in the 1994 report was lumped together, we need to rely on our experience and reports from the literature to determine AH's effect. In our experience, we were impressed by three very apparent findings.
- First, we discovered that there is a learning curve for this procedure that requires a certain amount of experience with the technique before patients can reap the maximum benefits.
- Our second conclusion was that assisted hatching not only improves the success rate of the patients with the poorest chance of pregnancy because of their age, previous failure or elevated FSH level, but it can also make these "poor prognosis" patients almost as likely to succeed as any patient going through in vitro fertilization.
- In our own experience, in 1995, 133 procedures on poor-prognosis patients yielded 57 clinical pregnancies (43%) and 46 live births (35%). A "take home baby rate" of 35 percent is very close to what we were achieving with our average patients at that time.
- As one would expect, we had the best "take home" baby rates in the under age 40 group with a success rate of 47% (64/138) ongoing or delivered pregnancies per retrieval in 1994, 1995 and part of 1996. During this period, ongoing and delivery rates were 23.1% at age 40 (6/26), 25% at 41 (10/41), and 44% (7/16) at 42.
- Thus, our third observation is that assisted hatching is most effective through age 42. We feel that patients over age 42 would be better served by egg donation if they are willing to accept the concept. It is important to remember that these observations are preliminary and made on the basis of a small number of cases and we will need the confirmation of our and other’s ongoing experience.
The bottom line for couples who fall into the "poor prognosis" category because of age (but under age 43), previously failed cycles or elevated FSH levels on the third day of their menstrual cycle is that they should consider adding assisted hatching to the regular regimen of in vitro fertilization. It is important to be sure that the center they choose has enough experience with the technique to assure they have passed the early part of the learning curve and are achieving an enhanced success rate. Finally, couples in which the woman has passed her 43rd birthday should consider egg donation as the most likely method to achieve success.
Excerpted from: CONCEPTIONS AND MISCONCEPTIONS: A GUIDE THROUGH THE MAZE OF IN VITRO FERTILIZATION& OTHER ASSISTED REPRODUCTION TECHNIQUES by Arthur L. Wisot, M. D. and David R. Meldrum, M.D. (Hartley & Marks Publishers, Pt. Roberts, Washington)
