MONDAY, Oct. 4 (HealthDay News) -- Using time-lapsed video to
watch fertilized eggs grow may offer clues about which embryos have
the best chances of resulting in pregnancy when using in vitro
fertilization, Stanford researchers report.
Under current techniques, embryologists look for certain
physical characteristics of the embryos at about Day 3 to decide
which embryos are thriving and should be placed in the woman's
uterus. That procedure usually occurs at around Day 5, when the
embryo has reached the blastocyst stage, considered a critical
stage of development that ups the chances of pregnancy.
However, research suggests that embryos grown outside of the
mother's body may be susceptible to changes in gene expression that
may raise the risk of some long-term health problems, said senior
study author Renee Reijo Pera, director of the Center for Human
Embryonic Stem Cell Research and Education at Stanford's Institute
for Stem Cell Biology and Regenerative Medicine in Palo Alto,
The new technique, which uses imaging technology and a computer
algorithm to observe and analyze the growth of embryos during the
entire first three days, could help IVF practitioners choose the
best embryos sooner, Pera said.
Being able to better predict which embryos will survive could
ease the pressure on couples and their doctors to implant multiple
embryos that can result in twins, triplets and higher order
multiples, Pera said.
According to the study, the timing with which the embryo divides
from one cell into multiple cells during the first three days can
predict with 93 percent certainty which embryos will make it to the
blastocyst stage, which indicates a healthy embryo.
The study is published in the Oct. 3 online issue of
With in vitro fertilization, the sperm and egg are joined
outside the womb to form an embryo. Typically, IVF practitioners
create several embryos, which are grown in a culture for three to
At that point, an embryologist views the embryos under a
microscope and selects those that look the healthiest for
Embryologists look for embryos that are plump and dividing
regularly; embryos that are small, dark or irregular probably won't
survive and attach to the lining of the uterus, Pera explained.
But the process of creating and choosing embryos is imperfect,
Pera said. Many embryos don't survive beyond the first few days --
about 50 percent to 70 percent of embryos don't make it to the
blastocyst stage, according to background information in the
Even for those that do, there's no guarantee of a pregnancy.
Nationwide, the live birth rate for each IVF cycle is about 30
percent to 35 percent for women under 35, and drops as a woman's
age increases, according to the American Pregnancy Association.
In the study, researchers filmed 242 one-cell human embryos that
had been frozen and donated to medical research. Of those, 100 made
it to the blastocyst stage at about Day 5.
'Movies' of the embryos developing showed that those most likely to make it to the blastocyst stage followed a similar pattern: it took about 15 minutes to complete the process of a single cell dividing into two cells; the third cell appeared between 7.8 and 14.3 hours; the fourth cell appeared shortly thereafter (within an hour).
"You want the third and fourth cells close together," Pera said. "If they are both healthy, you want them to be synchronous. If one lags, it's probably going to die."
An embryo that's made it to the blastocyst stage has a two- to
threefold greater chance of resulting in a pregnancy, Pera
Watching the embryo as it grows and divides offers a more
complete picture of its health than viewing the embryo only at a
single point in time, Pera said. "How the embryo moves, when it
divides, that's where the information is," Pera said.
Pera compared it to watching a person who is ill versus a
healthy person walk. "If you watch a person who isn't well cross a
road, you know they are not well," Pera said. "You can get all
kinds of clues from the movement compared to when they are standing
Dr. David Smotrich, medical director of La Jolla IVF in La
Jolla, Calif., said the research is promising.
"This is a very eloquent paper," Smotrich said. "If you are able to make this prediction early on, in theory you can choose which embryos to place much earlier and have a better understanding of the overall quality of the embryo and overall likelihood of it to implant."
Yet much more needs to be learned, Smotrich said. The study
looked only at what happens to embryos up to about Day 5. Since
none of the embryos were actually implanted, there's no way of
knowing if the technique would improve IVF success rates.
The imaging technique itself also needs to be tested to make
sure there's no risk of damaging the embryo, Smotrich said.
Auxogyn Inc., of Menlo Park, Calif., has licensed the technology
from Stanford, and Pera said the next steps are clinical trials to
determine if the screening method works outside of the lab.
U.S. National Library of Medicine has more on
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