Database size increase inside a transaction

I am using an SQLite database. I am inserting many rows in it, with insert statements inside a transaction.

However, I noticed (with step-by-step debugging) that before I commit the transaction, my database file increase in size, which means that some data have been inserted in it before the commit. And after the commit, it increases one last time, by a large amount (this one last thing is normal however).

Is this database size increase before the commit a normal behavior?