Finding out we were pregnant again was very stressful. We love Ben dearly, and he has brought our family so much joy, but all the same we worried about having another baby with CdLS. We understood that the recurrence rate for CdLS is fairly low, at 1-2% overall, but it was not zero. If anything, we were more likely to have a second child with CdLS than we were to have had Ben in the first place!
Most of the time, the mutation that causes CdLS is a sporadic event in the affected individual, and theoretically should not recur in a subsequent pregnancy. However, a few families do have more than one affected child. One possible explanation for how this happens is germline mosaicism in which one parent carries the mutation in the sperm or the egg but not in most of the other cells of the body. If germline mosaicism is present, then the recurrence rate for CdLS can be quite high; up to 50%.
It is a very personal decision whether or not to have special prenatal testing of a subsequent pregnancy to determine whether the new baby has CdLS. We opted to do this mainly for peace of mind, and to help us plan for the future if this new baby DID turn out to have CdLS, but we understand that many families may decide that the odds of recurrence are so low that special testing is unnecessary.
We had an ultrasound early in the second trimester, mainly to confirm my due date, and also to see if our new baby had any obvious limb differences. I had a routine quadruple screen blood test at about 16 weeks (which, incidentally, I never had with any of my previous pregnancies). I had a more detailed Level 2 ultrasound later in my second trimester. All of these tests turned out to be normal. If I had done my research earlier, I would have also requested a PAPP-A test as well. Low PAPP-A levels in the second trimester can be associated with CdLS.
The next big decision was whether or not to pursue more invasive genetic testing on the new baby. Genetic testing for CdLS is available through the University of Chicago Genetic Services Laboratory. We had already obtained a blood sample from Ben last summer, and his sample was sent to the University of Chicago for testing. A mutation was found in Ben’s blood sample in the NIPBL gene on chromosome 5, so it was possible to test the new baby for the same genetic mutation by obtaining fetal cells by amniocentesis. We opted to have this done (not an easy decision since amniocentesis has a 1 in 300 risk of miscarriage), and the amniotic fluid was sent to the University of Chicago along with blood samples from myself and my husband to be tested. None of the three samples had Ben’s mutation, so we are fairly certain that this new baby does not have CdLS.
In pregnancy there are no guarantees, and we still don’t know what special challenges our new baby may have. I am not sure how many parents of kids who have CdLS choose to have all of this prenatal testing for subsequent pregnancies. For us, having the tests helped to decrease our stress level considerably, and I am glad they were available, and that we had them done.