Thursday, August 6, 2015

It's All About the Genes

Today was our visit to the Genetic Counselor.  Please refer to the "Family History and Genetics" page for more information on who Genetic Counselors are and what they do.

Due to our unique situation there were three of us at this appointment - me, Mark and our GC.  Really only Mark and I needed to be there - it is our history and our genes that are in question.  But, our GC needed to get the referral and make the appointment since it is her pregnancy.  In the end, it good that she was there since we discussed screening and testing options and since she is impacted by our decisions regarding these it is good for her to also understand the risks.

I would never ask our GC to do something that I would not myself do.

We went through our family history and what our risks are.  Unfortunately, chromosomal abnormalities increase with age.  By the age of 40 the risk of a child being born with some sort of genetic abnormality is as high as 1/38.

Our family history can help predict which abnormalities we may carry and pass on.  For example, since Mark and I are both of Northern European descent, we are more likely to be carriers of Cystic Fibrosis.

Carrier screening can be done to tell for sure if you are a carrier of a specific disorder.  Most disorders are recessive meaning that both you and your partner both need to be carriers for a particular disease to present itself.  And even if you both are carriers, you may not pass on that disorder to your child.

Mark and I had not had carrier screening done.  We had asked our RE about it before our first IVF and he did not recommend it.  His logic was that everyone is a carrier for something.  Everyone.  And sometimes people make decisions about even having children based on these tests.  Again, being a carrier does not automatically mean that you will pass a disorder to your child.

Luckily we are early enough into the pregnancy that carrier screening can still make a difference on our prenatal testing choices, so we headed to the lab for a blood test right after our consultation.

Unfortunately, we did not have PGD or PGS testing (see Embryo Testing in IVF page for more info)  done on our embryos, so we do not know definitively that Maybe Baby is chromosomally normal.  We did not do PGD testing since we had not done carrier testing and did not know which specific genetic disorders to test for.  We also did not do PGD testing and additionally PGS testing since this needs to be done on day 5 blastocysts and we were not sure that we would end up with any day 5 blastocysts to test.  Maybe Baby was a day 5 morula and previously frozen, so testing was not recommended.

Our counselor went through our screening and diagnostic testing options.

As I have mentioned before, I like the idea of diagnostic testing.  It is definitive while screening is not.  It also carries risks.

I have been talked off the CVS ledge and am now leaning towards amniocentesis.  

Amniocentesis is a prenatal test that allows your healthcare practitioner to gather information about your baby's health from a sample of your amniotic fluid - the fluid that surrounds your baby in the uterus.  Amniocentesis produces a karyotype – a picture of your baby's chromosomes – so that your caregiver can see for sure if there are problems.  It is more than a 99% accurate test.
Amniocentesis carries various risks, including:
  • Miscarriage. Second-trimester amniocentesis carries a slight risk of miscarriage — between 1 in 300 and 1 in 500. Research suggests that the risk of miscarriage is higher for amniocentesis done before 15 weeks of pregnancy.  Our counselor indicated that the risk goes down significantly for practitioners that perform this test regularly and that this clinics risk rates were as low as 1 in 1500.
  • Needle injury. During amniocentesis the baby might move an arm or leg into the path of the needle. Serious needle injuries are rare.
  • Leaking amniotic fluid. Rarely, amniotic fluid leaks through the vagina after amniocentesis. If the leak seals, the pregnancy is likely to proceed normally. It's possible, however, for chronic leakage to lead to orthopedic problems for the baby.
  • Rh sensitization. Rarely, amniocentesis might cause the baby's blood cells to enter the mother's bloodstream. If you have Rh negative blood, you'll be given a drug called Rh immunoglobulin after amniocentesis to prevent you from producing antibodies against your baby's blood cells.
  • Infection. Rarely, amniocentesis might trigger a uterine infection.
  • Infection transmission. If you have an infection — such as hepatitis C, toxoplasmosis or human immunodeficiency virus — the infection might be transferred to your baby during amniocentesis.
Since our GC does not have any diseases to transmit (per testing), is RH positive to the RH factor risk is not there, infection can be easily treated with antibiotics, needle injury is rare as is leaking amniotic fluid and the risk of miscarriage at our clinic is as low as 1 in 1500, I still think that the benefits of amniocentesis outweigh the risks.

However, I have listened to our Genetic Counselor and Mark on utilizing noninvasive screening tests first.

We had the Harmony test done which is a simple blood test (of our GC's blood) that screens for the most common chromosomal disorders - 99%, but not all, of the fetuses with trisomy 21 (aka Downs Syndrome), 97% of fetuses with trisomy 18 and 92% of fetuses with trisomy 13.  The Harmony test also tests for gender and sex chromosome related disorders. The Harmony test does not provide information on other rare chromosomal abnormalities.  The Harmony test also does not provide information on physical defects, such as heart or brain abnormalities and spina bifida, or fetal growth.

It is therefore advisable that you still have ultrasound scans to screen for other potential defects - a scan at 11-13 weeks and at 18-22 weeks to examine the fetal anatomy and at 30-32 weeks to examine the fetal growth. 

Additionally, it is also advisable to also have a quad screen — also known as the quadruple marker test or simply the quad test — at 15 to 20 weeks of pregnancy  This test measures levels of four substances in a pregnant woman's blood: Alpha-fetoprotein (AFP), a protein made by the developing baby, Human chorionic gonadotropin (HCG), a hormone made by the placenta, Estriol, a hormone made by the placenta and the baby's liver, and Inhibin A, another hormone made by the placenta

Results of the quad screen indicate your risk of carrying a baby who has certain chromosomal conditions, such as Down syndrome, and can help detect neural tube defects, such as spina bifida.

We are scheduled for our 11-13 week scan next week.  This is the Nuchal Translucency Screening Test which screens for major defects, such as exomphalos, holoprosencephaly, heart abnormalities or megacysis, and some other rare chromosomal defects.  It uses ultrasound to measure the thickness of the fluid buildup at the back of the developing baby's neck. If this area is thicker than normal (more than 3.5 mm), it can be an early sign of major defects and further testing such as a CVS or amniocentesis may be recommended for actual diagnosis.

This test is noninvasive and basically just like a regular ultrasound.  The major difference is that it must be done by a specially trained ultrasound technologist, radiologist or obstetrician who has received special training to do this test.  Basically that you will probably need to go to a different clinic than your regular OBGYN.

We are then looking to do the quad screen at 15 weeks, another noninvasive test.  Our genetic counselor said that actually we don't need to do the full quad screen since we did the harmony test and parts of the quad screen would be duplicative.

We are then looking to do the anatomy scan at 18 weeks.

We will tentatively schedule an amniocentesis for 19 weeks, which will only be performed if an issue arises at one of our earlier tests.  Otherwise, we may be chancing risk that we would otherwise not need to undertake.

I think that this is a good plan as it utilizes as much noninvasive testing as possible. 

Each hurdle that we clear and test result that comes back good starts to make me more and more confident that Maybe Baby with become a real baby someday.

Right now is still early and we have a lot of tests to do, so I am staying only cautiously optimistic at this point.

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