–Belle has morning sickness but she is so newly pregnant that she didn’t even know she was pregnant when Rumple told her. But Zelena, who was pregnant for long enough to fully know she was with child, never had morning sickness? That makes NO sense.
Speaking from personal experience, I suffered from morning sickness just before I got a positive pregnancy test. It turned positive 14 days past ovulation, the most common day to get a positive. (This ended up as a chemical this Feburary, however). Meanwhile my friend who carried two boys to term never experienced nausea or morning sickness in either of her pregnancies.