Unfotonately there is no medical reason why there is no heart beat.Its usually due to a developmental anomaly.This is called blighted ovum
.She can start trying for conception after 2-3 mths,but its not possible to say why she couldnt conceive sooner after the first MTP
without more tests.Ask her to consult a fertility
specialist and plan the next pregnancy
if she has difficulty in conception next time.Some tests may need to be done.