Reproductive Endocrine Assoc. Assisted Reproduction Q & A

What is NEST?

NEST stands for "Nonsurgical Embryonic Selective Thinning and Transfer". It is a new treatment which was developed at our Institute, and is currently being studied.

Nonsurgical embryonic selective thinning and transfer is a technique for the active management of early embryonic growth and development. It utilizes newly defined growth media which facilitates embryonic cleavage. Selective thinning and transfer can be performed on the third day post ovum pickup when genetic competence may be more easily assessed on morphologic grounds. Unlike assisted hatching, selective thinning can also be performed on day 2 post ovum pickup, since the zona (the membrane surrounding the fertilized egg) is not fully breeched. The combination of embryonic thinning and selective transfer results in an increase in implantation rates, cycle fecundity rates, and overall pregnancy rates.

  1. Use of an optimized culture media for growing embryos. This media allows all embryos to grow to their fullest potential, helping us to distinguish genetically superior embryos, from those which will fail to thrive.

  2. Transfer of the healthiest, highest quality embryos on day 3 following the egg retrieval, if possible. Oftentimes, the culture of embryos for an extra day in the laboratory will expose subtle differences in quality between embryos that will help us choose the best ones for transfer.

  3. Micromanipulation of the cleaving embryo involving the use of assisted hatching or selective thinning of the zona. Assisted hatching can only be performed on the 3rd day of culture. Selective thinning can be performed on the 2nd day of embryonic culture, or even on the 3rd day, if assisted hatching is not clinically indicated.

In a pilot study presented at the 1998 Pacific Coast Fertility Society Meeting, we demonstrated that these combined steps produced a 58% pregnancy rate in 16 consecutive patients, versus 26% in a comparable "control" group.

A description of NEST can be found in the July 1997 issue of "Cosmopolitan" Magazine.

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