Page 1 of 2
Frequently Asked PGD/PGS Questions
1. What is the difference between PGD and PGS?
PGD stands for Preimplantation Genetic Diagnosis and refers to screening embryos for a particular
genetic disorder - for example, sickle cell disease.
PGS stands for Preimplantation Genetic Screening and refers to testing to ensure that the correct
number (46) of chromosomes are present - for example, to make sure that trisomies such as trisomy
21 that causes Down Syndrome are not present.
2. Will doing PGD/PGS increase my chances of pregnancy?
Pregnancy will depend on your situation and how many normal (euploid) embryos are collected during
the IVF cycle. However, it can be said with certainty that your chance of miscarriage is lower when a
normal embryo is transferred, since many miscarriages are the result of chromosomally abnormal
embryos.
The transfer of a normal euploid embryo does not guarantee pregnancy, because there are many
other factors involved in embryo implantation aside from the chromosomes. If you are doing PGD to
check for a single gene disorder, we recommend doing the 24 chromosome screening as well. The
two tests together have been shown to improve outcome and decrease miscarriage rate.
3. What happens to my embryos following biopsy - are my embryos at any risk?
We quickly freeze (vitrify) all embryos after biopsy. This allows us to keep them in a stable state until
testing is complete and for the embryo transfer to occur in an unstimulated Frozen Egg Transfer (FET)
cycle. Our long-standing experience with PGD/PGS means that we have senior embryologists who are
very skilled with embryo biopsy. Our embryos survive biopsy >99% of the time, with cryosurvival for
these embryos >96%. Furthermore, the cells we remove during trophectoderm biopsy are the cells
that will develop into the placenta, not the fetus itself. The inner cell mass, which develops into the
fetus, is not involved in the biopsy at all.
4. What is zona ablation?
The embryo is surrounded by a protective layer called the zona pellucida - similar to the protective
shell around a chicken egg. In order to be able to perform the biopsy, we must “crack” the shell safely
during development. This is accomplished by using a microscopic laser beam to create a hole into the
zona pellucida. This hole in the “shell” will allow for embryo biopsy.
5. Is there a minimum number of embryos needed for biopsy?
A patient can choose to biopsyembryos even if there is only one or two available, there is no minimum
requirement that needs to be met. An ideal number of embryos desired is dependent on the individual
patient and clinical situation and should be discussed with your physician directly.
6. Is it better to bank embryos?
Embryo banking may make sense for financial reasons, since there are certain laboratories that
charge “flat” fees for biopsy. The biopsied samples will be stored in the reference lab’s freezer
while the patient collects more embryos for biopsy in a subsequent IVF attempt. All embryos are
frozen after the biopsy and are stable indefinitely. However you will not be able to find out the
PGD results until you instruct the reference lab to run your samples.
Embryo banking is also a consideration for patients who have multiple embryos to be biopsied. In
most cases we recommend the transfer of a single normal (euploid) blastocyst and at most we will
only transfer two.
To determine if embryo banking is the right choice for you, please discuss your situation with your
physician and Billing.
FERTILITY CENTER at NYULMC
660 First Avenue, 5th Floor, New York, NY 10016 tel 212.263.8990  fax 212.263.7853  www.nyufertilitycenter.org
Form #2076 – Rev. 09/18/2014
Page 2 of 2
Frequently Asked PGD/PGS Questions
7. When will I get information on my embryos?
We biopsy embryos when they reach a certain stage- the biopsy of your embryos will happen on day 5
and/or day 6 and occasionally on day 7. Our lab does its best to reach out to patients after the
biopsies have been performed on day 6. However, we do not leave messages with information on this
matter (unlike when the nurses leave instructions). If you miss a call from the lab, you can call us back
at (212) 263-8990 between 9am – 5pm during the week. The on-call doctor will not know the details of
your biopsy, so please do not call after hours.
In terms of the results of the chromosomal testing for aneuploidy, the turn-around time is
approximately 2-3 days from the date the cells are sent out. For single gene defects, the turnaround time can be 2-3 weeks. That means it may be up to 2 weeks, or longer for single gene
cases, after your biopsy for us to receive the results, have the physician review them and for our
staff to contact you with the genetic results. Patients can choose to start medications for a frozen
transfer cycle prior to receiving the results of testing. However, if no embryos are chromosomally
normal, then patients will be advised to stop the medications at that time. In other words, the cycle
is cancelled and that may have a financial impact and further implications with the patient’s
insurance.
8. Does the quality of the embryos matter?
Yes, the embryos must reach a certain stage of blastocyst development in order to undergo
trophectoderm biopsy. Blastocyst quality is scored based on three respects:
1)
2)
3)
Degree of expansion
Quality of the inner cell mass that becomes the fetus
Quality of the trophectoderm which gives rise to the placenta
Embryos must reach a stage of sufficient development in order to physically undergo biopsy. For
example, non-expanded blastocysts cannot undergo biopsy because of the lack of cell differentiation,
meaning we are unable to distinguish the trophectoderm cells from the inner mass cells in these
embryos.
9. Why do we recommend freezing over fresh biopsy?
There is published literature suggesting that embryo transfer into a uterus that has not been exposed
to stimulation drugs results in better pregnancy rates. For this reason, we recommend patients opt to
freeze embryos at time of biopsy and proceed with transfer in a frozen cycle. The frozen cycle
immediately follows the retrieval cycle in many cases.
10. When do I have to decide if I am doing PGD/PGS?
PGD for a gene disorder requires coordination weeks to months in advance and depends on the
complexity of your case. The genetics laboratory must develop a “probe” for the specific genetic
disorder. This requires obtaining a sample from both you and your partner to evaluate the genetic
profile and to build a probe based on your chromosomes.
PGS should be decided upon prior to starting your cycle as you need to have a consult with the
genetics laboratory to discuss your situation and sign the appropriate consents and determine financial
arrangements.
Nothing is written in stone. You can change your mind and cancel PGD/PGS. A fresh transfer is
possible provided you are taking the appropriate medications following retrieval to properly prepare the
uterine lining. Be sure to discuss your options with your physician at the initial consultation.
FERTILITY CENTER at NYULMC
660 First Avenue, 5th Floor, New York, NY 10016 tel 212.263.8990  fax 212.263.7853  www.nyufertilitycenter.org
Form #2076 – Rev. 09/18/2014