What laws should the British royal family obey during pregnancy?

Some people believe that the child's gender can be diagnosed by her craving during pregnancy. If the mother wants to sweat, she's a kid, and if the passion for salty food is a boy. For this reason, pregnant women of the royal family should not eat anything in public, so that there is no rumor about the sex of their  child. The only exception to this rule is to attend a party in which a meal is served to all guests.