The reason for the speculation this time is due to a photo taken at the Royal Albert Hall Memorial Festival. Prince Harry and Megan were placed on a delicate dish, and this shows how Megan wears a dress that extends just above her waist.
Megan was able to conceal her first pregnancy well. So she always wore the right dresses and jackets to hide her growing baby belly. That's why fans are now paying extra attention to her clothing and posture.
The photo below also shows Megan putting her hand on her belly.