Recurrence (genetic mutation)
We are expecting our second child. We were told by our geneticist that if this new baby were to have CdLS it would be the exact same genetic mutation that our child with CdLS has (NIPBL). Is that true?
Congratulations on your new baby! Yes, if you were to have a second child with CdLS, we would expect that child to have the same exact NIPBL mutation as his or her sibling. The small chance (less than 1%) to have a second child with CdLS when the parents are unaffected is due to something we call gonadal mosaicism-meaning that the specific mutation could be present in a portion of eggs or sperm. This is really atypical or unusual (hence the less than 1% chance), but it would be from the same gene change or mutation. I kind of think of it as there being a typo in one of your child's NIPBL genes. Likely the typo just occurred at conception for your child. But, sometimes one egg or sperm has the typo and it gets copied into other eggs/sperm, (gonadal mosaic). If that egg or sperm is then used for a pregnancy, we would see second child with CdLS. But since your amnio was normal, we can be assured that did not happen.
I assume they asked to see your first child's test results when they did your amnio so they knew what they were looking for and asked you for blood for something called "maternal cell contamination"- sometimes we send mom's blood with amnio sample when we are doing any kind of genetic testing.
Bottom line is-I would feel extremely reassured by your results. At this point, your chance for a pregnancy with CdLS is no greater than any family out there in the general population. We have eliminated that increased risk based on your first child having CdLS.
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