Well, the flashbacks are shown out of order.
If you notice, EQ threatens Snow and Charming on their wedding day, but by the time she enacts the Dark Curse, Snow is ready to give birth, so at least 9 months passes between the time EQ threatens them and when she actually goes through with it.
Rumple was imprisoned sometime in between when EQ threatens SW/Charming at the wedding and when EQ goes to vistit him about why the Dark Curse didn’t work.
Rumple being imprisoned happened when Cinderella was visibly pregnant.
Her and Snow seemed to be pregnant around the same time, considering that Snow gave birth right before the curse hit, and Cinderella was still pregnant in SB (technically, she was pregnant for 28 yrs) but then gave birth shortly after Emma arrived in SB and things started to change.