thanks for your query.
The HCG values should double within 48 hours, hence the declining levels suggest that the pregnancy
is non viable.
it indicates an impending miscarriage
itself will not assure that the pregnancy is viable.
if you have a miscarriage, then ensure that the products of conception are sent for karyotyping.
Once this pregnancy is terminated, wait for atleast 6 months before planning your next pregnancy, after having thorough preconceptional counselling
All the best.