HI,
Thanks for choosing HCM
in your question you told"but  there is fetal viability "
is it "fetal viability" or "no fetal viability"?
reason for prescribing 
folic acid is for good development of fetus and to avoid neural tube defects(brain  and 
spinal cord defects)
The other is 
dydrogesterone duphaston
it is orally active progestogen used treatment of recurrent 
pregnancy loss, and for prevention of preterm birth in pregnant women with a history of at least one spontaneous preterm birth.
so in your case to avoid complications like 
miscarriage it is given so that hormonal imbalance gets corrected
please continue 
dont worry ,dont let stress cause pregnancy loss
go for next scan at scheduled time and talk to your doctor
meanwhile you can continue the medication without doubt
hope i answered your queries
feel free to contact me for further queries
thank you