A Guide to Genetic Testing for Surrogate Pregnancies
When we talk about "genetic testing for surrogate pregnancies", it can refer to several genetic tests done during the process: those done on the egg donor, on the intended parents (screening for recessive genetic conditions), on the embryo pre-implantation (PGS or PGD) and tests targeted at the developing embryo/fetus once pregnancy has been achieved. I will focus on the latter, today: the tests that may be offered to you/your surrogate at the early stage of the pregnancy to screen for Down syndrome and other chromosomal problems. Although there are many types of genetic problems that can affect the human chromosomes, the main concern is Down syndrome (AKA Trisomy 21) because it's the most common genetic abnormality for babies born around the world. Because the risk of Trisomy 21 (T21) increases with the age of the genetic mother (or egg donor), two invasive diagnostic modalities have been made available to women, particularly those above the age of 35. These tests are called chorionic villous sampling (CVS) and amniocentesis. They are referred as diagnostic tests because they can diagnose T21 with 100% accuracy). They are "invasive" because there is a small risk that the procedure (which involves a needle that traverses the uterus) will lead to a miscarriage, at a frequency of about 1 for each 200-500 procedures performed (depending upon who does it and where it is done). I have been doing amniocentesis and CVS for 20 years.
Screening tests for chromosomal abnormalities, however, do not involve any risk and they only involve either (or both) an ultrasound and/or a blood test. The nuchal translucency test is performed at about 12-13 weeks, and is accompanied by a blood test. It can detect up to 91% of T21 fetuses, but there will be a false positive in about 5% of normal pregnancies (meaning, 5% of normal pregnancies will have a nuchal test suggesting a high risk of T21 even though the baby is fine, which is often followed by amniocentesis or CVS). The quad test, performed at 16-18 weeks, is sometimes performed following the nuchal translucency and slightly improves the detection of T21. It’s sometimes (but rarely) performed on its own, without the nuchal translucency test.
The tests that have been getting more attention lately are the cell-free DNA tests (AKA: non-invasive prenatal testing, NIPS, non-invasive prenatal screening) and commercially known as Harmony, MaterniT21, Verify, Panorama, and others too. Let’s refer to this test as NIPS. About these NIPS tests: they can not only detect over 99% case of T21, but do so at a false positive rate of less than 1%. That’s really good. However the false positive rate is somewhat higher in young women, which leads many authorities and HMOs to only recommend (and pay for) the test in pregnant women who are at least 35 years old. It is an expensive test. My hunch is that very soon, this non-invasive test will be offered to ALL pregnant women, regardless of their age, and all insurance plans will pay for it, but we’re not there yet. The companies that offer the various NIPS testing (like Panorama, Harmony, MaterniT21, etc…) use techniques that are slightly different from one another, so some of those tests cannot be used in a pregnancy where there is an egg donor involved. Also, although some NIPS tests claim they do well with twins, the test is NOT as powerful in detection T21 in twins versus singleton. The same goes for all the screening for T21, actually.
So in summary, when deciding about doing NIPS or an invasive test such as CVS or amnio:
The risk of T21 is never zero. Even if your egg donor is 21, the risk of T21 and other chromosome problems is very very low, but not zero.
If you decide to have CVS or amniocentesis, in addition to testing for T21, you may be able to detect chromosome problems which are rare but significant, and are not routinely part of non-invasive screening tests. (That’s definitely an advantage). But CVS or amnio comes with a risk of miscarriage, low, but real. After all you’ve been through, is it a risk you want to take?
The age of the surrogate has nothing to do with the risk of chromosome problems. Ditto for the age of the intended father’s sperm. The age of the egg donor is pretty much all that matters.
If you opt for NIPS, chose a NIPS test that can be performed in egg donor IVF. Ask your OB.
NIPS can be done at any time during pregnancy, starting as early as 9 or 10 weeks.
NIPS will reveal the baby’s gender with 99% accuracy.
Be prepared for possibly having to pay for the test if your egg donor (or intended mother) is 35 or younger. That’s the norm; we have young egg donors. The gestational carrier’s insurance may deny payment.
If you have twins/multiples I think that for the time being, nuchal translucency (at 12-13 weeks) alone or with quad screen follow up (modified sequential) at 16-18 weeks is the best option.
Even if your embryo was screened by PGS, we still recommend considering the above screening or diagnostic tests, as the PGS technology is not a perfect one, and chromosomal anomalies have been observed in embryos originally screened as normal.
This is a guest post from Georges Sylvestre, MD. Dr. Sylvestre is an OB/GYN specializing in high-risk pregnancies. He also serves on the Board of Directors for Men Having Babies, which provides surrogacy advice and support for gay men worldwide. Thank you Dr. Sylvestre for sharing this information with our readers. This post offers neither legal nor medical advice. Please discuss this issues with your own doctor and lawyer for advice appropriate to your situation.
Interested in becoming an intended parent? Interested in becoming a surrogate? Contact us today to learn more.