In standard American English we keep the -ing ending, regardless of what the next word is. However, there are some fairly common dialects in which people replace the -ing ending with-in. They also do this regardless of what the next word is.

The "g" becomes a nasal sound that can be continued indefinitely, like humming. There is no link to the next word. In dialog, authors will sometimes omit the "g" and replace it with a apostrophe in order to make it sound different. Thus you can write: "reproducing it" or "reproducin' it" In the first you have a nasal sound. In the second you have no nasal sound and the "n" is linked to the "it".