guppies

i Have a femal guppie and a male guppy but they have not gave birth to any babys yet why is this

Guppies that are bought in pet stores are often raised in poor conditions, are often hybrids and are inferior in quality to the more expensive guppies that are bought for the purpose of breeding.

One result might be that the male is sterile or that he is too old to have any real interest in breeding.

There can be many other reasons relevant to the tank that you have the p.h the food the water circulation.

If you need a more concrete answer I'd like to have more details.