Preimplantation Genetic Screening (PGS)

24-Chromosome Aneuploidy Screening with Parental Support™

Improve your chance of pregnancy and of having a healthy baby.

PGS testing is done as part of an in vitro fertilization (IVF) cycle. The purpose of PGS is to raise your chance of becoming pregnant and lower the chance for miscarriage after embryo transfer.

PGS tests for the number of chromosomes in one or a few cells from each embryo of an IVF cycle. Embryos with the normal number of chromosomes (46) have a better chance of implanting and creating a healthy pregnancy. After PGS testing, these embryos can be selected for transfer to the mother’s uterus.

Extra or missing chromosomes can happen in any embryo due to an error when the egg or sperm cells are being made, or during early development of the embryo.

Most embryos with an abnormal number of chromosomes either do not implant or result in miscarriage. Depending on the type of chromosome abnormality, they may result in the birth of a baby with a chromosome syndrome. For example, Down syndrome is caused by an extra copy of chromosome 21.

PGS testing lets you and your IVF doctor choose the embryos most likely to have the normal number of chromosomes. When these embryos are chosen for transfer, there is a higher chance of implantation, a lower chance of miscarriage and a lower chance of having a baby with a chromosome syndrome.

The Science Behind the Test

Chromosomes and Chromosome Abnormalities Defined

Male and Female Karyotypes

Chromosomes carry our genes. The normal number of chromosomes in each cell of our body is 46. Chromosomes come in 23 pairs. There are 22 pairs of ‘autosomes’ (pairs 1 through 22) and one pair of ‘sex chromosomes’ (XX in females or XY in males). Thus, there are 24 unique chromosomes in humans, the 22 autosomes, X and Y. This is why PGS that tests all of the chromosomes is called ’24-chromosome screening’.

  • Having more or less than the normal 46 chromosomes is called a ‘chromosome abnormality’. Another term for having too many or too few chromosomes is ‘aneuploidy’.
  • Having an extra chromosome (47 instead of 46) is called ‘trisomy’. A missing chromosome (45 instead of 46) is called ‘monosomy’.

Most embryos with extra or missing chromosomes either do not implant in the uterus or are lost in early miscarriage. In fact, over half of all early miscarriages are caused by chromosome abnormalities.

In some cases, a baby can be born with an abnormal number of chromosomes. Babies with a chromosome abnormality have a specific pattern of intellectual disabilities and birth defects called a ‘chromosome syndrome’.

Chromosome abnormalities that can occur in liveborn children are:

  • Trisomy 21 (Down syndrome)
  • Trisomy 13 (Patau syndrome)
  • Trisomy 18 (Edwards syndrome)

Extra or missing sex chromosomes are seen in:

  • Klinefelter syndrome (XXY)
  • Turner syndrome (X)
  • Triple X syndrome (XXX)
  • Jacob's syndrome (XYY)

Other chromosomes can have extra or missing copies as well. These embryos almost never create ongoing pregnancies.

Extra or missing segments of a chromosome, called deletions and duplications, can also cause miscarriage or birth defects and intellectual disability. Natera is able to test for large missing or segments of each chromosome with PGS.

Benefits of Natera’s 24-chromosome PGS with Parental Support

If your doctor recommends preimplantation genetic screening (PGS) during your IVF cycle, our unique testing method using a SNP microarray and Natera’s Parental Support™, offers the most complete and accurate screen of all 24 chromosomes. With results typically greater than 99% accuracy, it is a test that both you and your doctor can depend on.

Natera’s 24-chromosome PGS:

  • Screens for extra or missing chromosomes of any of the chromosome pairs
  • Screens for large missing or extra segments of each chromosome
  • Can tell if the extra or missing chromosomes came from the egg or sperm.
  • Can find other abnormalities that other PGS technologies such as FISH or array CGH (aCGH) cannot:
    • Haploidy – a complete missing set of chromosomes leaving only 23
    • Triploidy – a complete extra set of chromosomes for a total of 69 (aCGH will miss some forms of triploidy)
    • Uniparental Disomy – some forms of UPD cause serious genetic conditions
  • Is the only PGS test that can confirm the correct parents for an embryo. If there’s a question about which sperm and eggs were used to create an embryo or if you just want reassurance that your eggs and sperm were used correctly for fertilization, our test always confirms parentage during our PGS testing.
  • Reports calculated accuracies for each chromosome result

Board Certified Genetic Counselors on Staff

Natera has a staff of board-certified genetic counselors available for phone consultations. These scheduled phone calls will give you more information about Natera’s PGS and answer any questions you have before you decide whether it’s right for you. To schedule a phone consultation, please have your IVF doctor send in a referral form and then call Natera at 1-877-476-4743.

Is 24-chromosome PGS right for me?

Chromosome abnormalities happen more often as a woman ages. They can also occur in any embryo just by chance. 24-chromosome PGS may be helpful to anyone who wants to improve their chance of having a successful IVF cycle.

If you are going through IVF, 24-chromosome PGS may be especially helpful if you:

  • Are considering a single embryo transfer
  • Are a woman age 35 or older
  • Have had one or more IVF cycles that did not result in a baby
  • Have had two or more prior miscarriages
  • Have had a prior pregnancy or child with a chromosome abnormality
  • Want gender selection because you are a carrier for an X-linked genetic disorder

Studies have shown that Aneuploidy PGS can increase IVF success in women who answered yes to one or more of the questions above. Since aneuploidy can occur in any embryo by chance, PGS for aneuploidy can be advantageous for anyone who wants to improve their chances of having a successful IVF cycle. The chance for aneuploidy also increases with a woman’s age.

Natera offers the most advanced technology available for preimplantation genetic screening for aneuploidy. We recommend that you talk to your doctor about the benefits and limitations of testing.

How Do I Get Natera's Testing?

Talk with your IVF doctor about the benefits and limitations of PGS. If your doctor doesn’t offer Natera, please have them contact Natera at 1-877-476-4743 so that we can set up an account with your IVF center. They can then refer you as a patient, and you’ll follow the same steps described below.

What are my Next Steps?

  1. Ask your IVF doctor for Natera PGS testing and have him/her send in a referral
  2. To find out more about PGS, schedule a phone discussion with a Natera board-certified genetic counselor (optional)
  3. Either your IVF clinic will give you a parent sample collection kit or Natera will send one to you.
  4. Complete your parent sample collection kit and send to Natera or have your blood drawn at your clinic.

FAQs

Additional FAQs about Preimplantation Genetic Screening (PGS)

When is PGS done?

PGS testing is done during IVF. The sample to be tested is taken a several days after fertilization by removing a single cell or cells from a developing embryo. Samples from each embryo are then sent to Natera for testing. The embryos themselves are frozen and remain at your IVF center.

PGS can be performed at two different times after an egg is fertilized, either the 3rd (Day 3) or 5th day (Day 5) day after the egg is fertilized. Results are available within one week.

  • In Day 3 testing, one cell, called a blastomere, is biopsied (removed) from each embryo.
  • In Day 5 testing, a few cells are biopsied (removed) from the tissue that will become the placenta (called the trophectoderm, or TE). This is the most common day for biopsy and PGS testing.

Day 5 testing is the most common type of PGS testing at Natera.

If you choose to have Day 5 PGS testing, a cluster of two to ten cells will be removed from the group of cells that will become the placenta. This is done at your IVF center by their embryologist. A biopsy is done for each embryo that will be tested. Each embryo sample is then shipped to Natera for testing.

The embryos themselves are then frozen at your IVF center until results are available. Results are returned to your IVF doctor within one week. Once you and your doctor have the chromosome results for each embryo, they can be thawed and transferred in a future IVF cycle.

The benefit of Day 5 testing is that Natera has more than one cell to test from each embryo. This gives results with higher overall confidence levels than Day 3 results. In addition, the risk of mosaicism is lower in Day 5 embryos.

Not all IVF Clinics perform Day 5 biopsies so please check with your IVF center if you are interested in more information about this option.

What are my chances of having embryos with chromosome abnormalities?

Extra or missing chromosomes can happen in any conception or pregnancy, simply by a chance error in how the egg, sperm or early embryo formed. However, the chances increase with the age of the mother.

About 1 in every 500 liveborn babies is born with a chromosome abnormality. The rate of chromosome abnormalities in embryos is much higher. About 35% of embryos in women under age 35 and over 70% in women over 40 years of age will show chromosome abnormalities in a day 5 sample. This is because most chromosome abnormalities cause the embryo to fail to implant or to miscarry, often before the woman knows she’s pregnant. This is likely the reason that women, as they age, have more problems becoming pregnant. The rates of chromosome abnormalities in embryos and liveborns is seen in the chart below.

Chance of Chromosome Abnormalities in a Day 5 Embryo
Maternal AgeAneuploidy Risk
Day 5 embryosLivebirths1
30 years and younger33%<0.5%
30-34 years35%<0.5%
35-39 years48%0.5-1.5%
40-45 years73%1.5-5%

1 Adapted from: Hook EB, 1981, Obstet Gynecol; 58:282.

If I do testing, what is the chance that all my embryos are abnormal and I have nothing to transfer?

Whether or not an embryo is transferred following testing depends on a number of factors:

  • The number of embryos available to test
  • The number of embryos that developed well enough to transfer
  • The chance of chromosome abnormalities based on maternal age and other medical factors

This graph shows the percentage of cycles with at least one embryo with normal chromosome results based on maternal age.

Percent of cycles with at least one embryo with normal chromosome results
Percent of cycles with at least one embryo with normal chromosome results

15,685 Day 3 embryo; 2,379 Day 5 samples. Data as of January 2012.
Data includes donor cycles; donors are all younger than 36.

If you want to discuss your personal chance for a normal embryo result, please have your IVF doctor send in a referral and then call Natera to schedule a phone consultation with one of our board-certified genetic counselors.

What are my chances of getting pregnant after using Natera’s PGS?

There are many different factors that influence whether or not you will become pregnant during your IVF cycle.

With Day 5 testing, Natera is seeing on-going pregnancy rates of about 60% overall when one or more embryos with normal chromosome results are transferred. The rate in patients under age 36 is about 65%. The rate in patients 36 and older is closer to 60%.

We are using an egg or sperm donor. Can we still do 24-chromosome PGS?

Yes, in almost all cases. In order to do PGS, a DNA sample (blood, cheek swab or sperm) is needed from the egg or sperm provider. If a donor is being used, your IVF clinic can coordinate collecting and sending this sample to Natera.

Do I need to have prenatal diagnosis (CVS or amniocentesis) if I have PGD or PGS?

Prenatal diagnosis - either by chorionic villus sampling (CVS) or amniocentesis - is strongly recommended to couples who have PGD or PGS. Although highly accurate, neither PGD nor PGS is 100% and it cannot detect chromosome mosaicism. Prenatal diagnosis can confirm normal chromosomes in the baby.

Will PGD or PGS guarantee a healthy baby?

No. There is a 3-5% chance in any pregnancy of having a child with a birth defect or intellectual disability, regardless of any testing performed before or during pregnancy. Many of these conditions cannot be found prior to embryo transfer or even during pregnancy. Parental Support detects the birth defects caused by extra or missing chromosomes. It cannot detect other structural chromosome abnormalities, such as balanced translocations or small rearrangements of chromosome material.

Also, as with all types of PGS, Natera’s Parental Support does not test for changes (mutations) within a single gene unless specifically requested. Thus, PGS it will not identify any single gene disorders such as cystic fibrosis, muscular dystrophy, or Tay-Sachs disease. And, PGS cannot detect common conditions such as autism, cleft lip, or heart defects.

If you know you and/or your partner are carriers for gene mutations causing a particular genetic disorder and want to know whether Natera can set up a custom preimplantation genetic diagnosis (PGD) test for that condition, please contact us.

Does the biopsy harm the embryo?

Removing one cell on Day 3 or several cells on Day 5 for testing does not appear to harm fetal development. Embryo biopsy has not been found to cause increased risk of birth defects. However, it is a newer test and there is still a chance for unknown effects.

Day 3 embryo biopsy without also doing PGS has been shown in some studies to have a lower chance of implantation. However, most doctors feel that if the biopsy is done correctly, doing PGS and then transferring embryos with normal results actually raises the chance for implantation.

I’ve had multiple miscarriages and am now considering IVF – how do I know if PGS will help me?

Couples with two or more miscarriage have been found to have a higher number of embryos with chromosome abnormalities in studies. Some studies have shown a higher rate of pregnancy, lower chance for miscarriage and higher rate of livebirth for couples who used PGS.

Before choosing PGS, couples who have had 2 or more miscarriages should talk with their doctor about having their own chromosomes tested to rule out inherited chromosome rearrangements. This can be done with a simple blood test. In about 5% of couples with more than one miscarriage, one person is found to have a balanced chromosome rearrangement. This does not affect that person’s health, but it increases the chance for miscarriage and for having pregnancies or children with chromosome abnormalities.

If a chromosome rearrangement is found, Natera has a special PGD test (translocation/inversion PGD) that can test each embryo of your IVF cycle for ‘unbalanced chromosome rearrangements that can occur due to your specific chromosome rearrangement.

Does Natera’s 24-chromosome PGS check to see if the embryos are actually mine?

Yes, because we use genetic information from the parents to compare to embryo results, we automatically confirm that the embryo cells match the parent samples. In fact, we are unable to issue a report if the biological parents do not match the embryo samples that were sent.

Why is knowing whether a chromosome abnormality came from the mother or the father important?

Natera’s Parental Support testing is able to tell whether a missing or extra chromosome came from the mother or the father.

This can be important when looking for patterns of chromosome abnormalities. Some of these may suggest a chromosome rearrangement in one of the parents. Knowing if the extra or missing chromosomes came from the egg or the sperm can help IVF doctors talk with couples about the best plan for future IVF cycles.

Do I have to use ICSI for PGS?

ICSI (Intracytoplasmic sperm injection of the eggs) is when a single sperm is used to fertilize each egg in an IVF cycle. ICSI is encouraged during your cycle if you’re using 24-chromosome PGS. However, it is not required.

Overall, it is better if you use ICSI. In a number of embryos where ICSI was not used, we have found an extra set of chromosomes that came from an additional sperm. This is called sperm contamination. In these cases, we cannot tell you the chromosome results on that embryo.

Natera recommends that you use ICSI during your cycle to eliminate the risk of sperm contamination, however, we do not require it for couples interested in PGS.

What if I have more questions?

You can ask your doctor to send in a referral. Then you can call Natera at 1-877-476-4743 to schedule a phone consultation with one of Natera’s board-certified genetic counselors.

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