We have heard from the geneticist. The news is not bad, but rather uncertain.

Here's the technicalities. Hannah has an extra chromosome on half her cells, as Janet mentioned earlier. There are two factors in Hannah's situation: which chromosome has the extra pair, and the fact that it's not on all cells.

Human chromosomes come in pairs. There are 23 pairs, yielding a normal 46 chromosomes. Down Syndrome, for instance, results from having an extra chromosome on pair 21. So it's important to know that Hannah has an extra chromosome (actually, a part of a chromosome--not even a whole extra one, which is really unusual) on pair 14. This is called trisomy 14. Since she has it only on part of her cells, it's also called mosaicism. So the complete condition is trisomy 14 mosaicism.

Had she had trisomy 14 on all cells, she could have suffered from facial abnormalities or hydrocephaly (water on the brain). With the mosaicism, the effect is lessened, and perhaps even absent.

Just to complicate things, there is this: the sample was a blood sample, of course, and with mosaicism there is no way to know if the same percentage holds with the rest of her body. It is quite possible for her to have no abnormal cells in her brain whatsoever, and that's what the geneticist is really wondering about at this point, because that's what could cause developmental challenges. If they are there, we may not be able to identify them until she is one or two years old--or even five years old.

So this is like waiting for the other shoe to fall, and (we hope) it may not fall at all.

Also making it difficult or impossible to come up with a prognosis: they've never seen this before. Our doctors knew of no record of a baby being born with trisomy 14 mosaicism. (The literature identifies some who were detected prenatally, but they either did not survive or the trisomy 14 did not show up in the baby--only in amniotic fluid or the placenta.) In subsequent searches, we have found a few references (such as a two-year-old girl), but they are very rare.

We'll go talk with them in more detail on Nov. 10.