Testing

You may know I'm 10 weeks pregnant with Nathan's sibling. If you didn't know, you do now. I spoke recently with the genetics counselor we met shortly after Nathan's birth. We reviewed some things she'd told us 4 years ago. At that point I understood myself to be at elevated risk for Down Syndrome, but did not understand about other trisomies. Parents who have had one child with a trisomy are at elevated risk for another. I'm told the risk is 1% that we could have a second child with a trisomy, and that this risk applies not only to trisomy 21 (Down Syndrome), but also to trisomy 18 (Edwards Syndrome), trisomy 13 (Patau Syndrome), etc. I of course want a healthy baby, but I am not overwhelmingly concerned about Down Syndrome. Been there, done that, could do it again. Somebody with Down Syndrome has brought a great deal of joy to my life and continues to do so every day. Trisomies 18 and 13 are more severe. Only 10% of babies with trisomy 18 or 13 make it to the end of their first year of life, so if I had to choose a trisomy from those options, I'd take 21 any day.

One of the major decisions we face with a pregnancy involves prenatal testing. To test or not to test? And which tests? There are initial blood screening tests, which carry no risk to the baby but come with a 5% false positive rate and a 15% false negative rate. In other words, these are screening tool, not a diagnostic test. This was the type of tool (though it's a bit more advanced now) that missed Nathan's trisomy 5 years ago. Amniocentesis is diagnostic, but carries approximately a 1:300 chance of causing a miscarriage (I have seen figures ranging from 1:200 to 1:500). CVS (chorionic villus sampling) is diagnostic and can be used earlier than amnio, but carries a 1:100 risk of miscarriage. Ultrasound is not diagnostic but can often pick up physical features of trisomies. There has been no demonstrated fetal harm from the use of ultrasounds; they are regarded as safe, though there is no evidence as to whether repeated exposure to ultrasound could be in any way detrimental to a fetus. In Nathan's case, nothing was picked up on ultrasound, but presumably a more severe heart defect would be caught, or a severe brain defect, or spina bifida.

Sooo... where am I going with this? If you've heard me discuss prenatal testing before, you will probably be completely unsurprised to hear me say I'm not having an amnio or a CVS. I've had miscarriages and I've got a kid with Down Syndrome, so I've experienced both those things, and the risks are not equal to me. I'll take the risk of Down Syndrome over the risk of miscarriage any day. The idea of trisomy 13 or 18 does concern me more: it seems like it would be very hard to be pregnant and know that I have a choice to say goodbye now or say goodbye later, and either way it's much too soon. If you're in the mood for a good cry, view the Trisomy 18 photo archives here. I would like to warn you first that many, many of these are babies "born into heaven", or who died soon after birth. Trisomy 13 is rarer but similar in terms of severity and life expectancy. It is my great hope not to ever have to face one of these diagnoses. It would be hard.

I had planned to do just the blood screening since it does not involve any risk to the baby, but talking with my my OB and the genetics counselor has changed my mind-- I'm not seeing the sense in taking a highly inaccurate screening test if I don't plan to follow up with a more accurate diagnostic test in the event of a positive result. So the plan then is this: I will have my 20 week ultrasound in 10 weeks, when it is time for that. The genetics counselor will review it. If there are abnormalities, we'll discuss them at that point. If not, we'll proceed on with a pregnancy that will hopefully go another 20 weeks or thereabouts-- I'm hoping for a full term baby this time around.