What to do if you're pregnant and have no appetite
First tell your doctor or midwife. They may have some recommendations or ask you more questions to determine the "why".
Otherwise I'd say during the first trimester it is pretty normal due to nausea and morning sickness.
Even in the third trimester it might be on the normal side as the stomach is pushed up and the general feeling of fullness takes over.
Eating smaller meals more frequently may help.