tingwong,
Please do not blame yourself. You must understand the development of a human being is a very complicated process, no man on earth can engineer a baby as of today (not even the clones). If it has to abort, it has to & there is nothing you can do to stop it.
Crying over it is natural & you (& your husband) should let out your feelings. I once saw a program on TV suggesting people like you who lose your baby should mourn properly - that includes, seeing the baby, touching it, keeping a lock of hair for memory for example, naming it & burying it. Then you won't feel guilty of not doing certain things when it is too late.
As for the biopsy, personally I may not suggest u to do it. Afterall, it is a fact. But if this baby is a boy, u may consider doing it to find out if genetically, you & your husband's genes may not favor a boy for some reasons. A friend of mine has similar experience. Her baby was born as a blue baby (at full term 40 weeks). Subsequently, they found out it had something to do with their genes but they were very brave to try for another girl & boy afterwards. So as long as knowing the fact would not be a hindrance to you for trying to conceive again, then do it. Otherwise, think twice.
Anyway, I wish you & your family can get over it quickly & treasure your daughter.