Most of what the geneticist told us we already knew. But it was still nice to hear it "officially." Here's what we discussed:
1) There are three types of Down syndrome.
- Nondisjunction. Occurs when either the egg or sperm has 2 copies of chromosome 21. When fertilization occurs the extra chromosome causes Down syndrome. This accounts for 95% of all cases of Down syndrome
- Translocation. Occurs when a part of chromosome 21 breaks off during cell division and becomes attached to another chromosome. This accounts for 3-4% of cases of Down syndrome.
- Mosaicism. Occurs when the error in cell division happens *after* fertilization. This causes some cells to have a third copy of chromosome 21 while other cells are normal. This accounts for 1-2% of cases of Down syndrome.
Daniel has nondisjunction Down syndrome. We knew based on the karyotype results that it wasn't mosaicism, and we were fairly certain it was nondisjunction but we wanted to hear that for sure. It doesn't matter in terms of his development, but if it were translocation my odds of having another baby with Down syndrome jump to 1 in 10. That would play a HUGE part in our decision to have/not have more kids.
2) In any case, my odds of having another baby with Down syndrome are still raised. Based solely on my age, my risk is about 1 in 1000. Now, because I've had a baby with Down syndrome, my odds are 1 in 100. However, the odds are not higher for my siblings or my children.
3) People with Down syndrome are more likely to develop autoimmune problems including thyroid problems, diabetes, and celiac disease. They are also more likely to develop leukemia, but the chances of that are still low. Vision problems are common (60% of children with Down syndrome) as is hearing loss (75% of children with Ds.) So far Daniel has no problems with any of these things, but we'll be testing regularly.
4) Physical characteristics are not an indicator of the degree of intellectual disability he'll have.
We spent an hour or so with the geneticist, his assistant, and a resident who was sitting in. They were great. They answered all our questions and were not at all patronizing or condescending (two things I hate.) And there you have it! Next up, our visit with the doctor and therapist.