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Factor IX- Severe runs in my family and I was diagnosed with FIX mild. What concerns should I have for getting pregnant. Risks to me or to my child that may or may not have hemophilia or bad. (My family has both)

May 16, 2019
Appreciates (347)

Hemophilia B (FX IX) occurs in 1 in 25,000 boys. The severity type is associated with the inherited variant and does not change per generation. Of course there is some difficulty in measuring levels particularly if it is between <1% and 1% which takes a high quality lab to consistently discriminate between those levels. If your father has hemophilia B, then you are an obligate carrier, meaning you definitely carry the genetic variant on the X chromosome while having a normal FIX gene on the other unaffected X chromosome. The risks of bleeding during pregnancy is related to the FIX level and most carriers (based on studies) with levels >60% during pregnancy have little pathologic bleeding. The bleeding tendency is more variable when <60%. Additionally FIX does not rise during pregnancy (it may rise 5% or so) and thus what your factor level is in the first trimester will be the same at the time of delivery. So if you are a carrier then your son has a 50/50 chance of having hemophilia B (mild) and the risk of bleeding in the newborn period is small for mild deficiency, with a very low risk of bleeding in the head. If you have a daughter she has a 50/50 chance of being a carrier and only in extremely rare situations would her level be low enough to lead to bleeding. The bottom line is you should go to an adult hematologist at your local HTC to get a birth plan in place.

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