What is NEST?
NEST
stands for Nonsurgical Embryonic Selective Thinning and Transfer.
It is a technique for the active management of early embryonic
growth and development. It utilizes newly defined growth media
that 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, it was demonstrated that these combined steps
produced a 58% pregnancy rate in 16 consecutive patients,
versus 26% in a comparable "control" group.
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