Catherine, the Duchess of Cambridge, hopes she is pregnant with a boy.
The royal is expecting her first child later this year and, while handing out symbolic shamrocks to members of the Irish Guards at the annual St Patrick's Day ceremony on Sunday, Catherine revealed she wants a son while her husband, Prince William, is hoping for a daughter.
Guardsman Lee Wheeler said: "I asked her do you know if it's a girl or a boy and she said, 'Not yet'.
"She said, 'I'd like to have a boy and William would like a girl'.
"I asked her if she had any names and she said, 'No'."
Catherine also told Sergeant Thomas Laven she was prepared for many sleepless nights.
It was recently claimed the couple are expecting a girl, after a well-wisher presented her with a white teddy bear during an official visit to Grimsby, north England and she said: "Thank you, I will take that for my d... for my baby."
Sandra Cook, who was standing next to a woman who gave Kate the cuddly toy, said: "As she handed it over I distinctly heard Kate say, 'Thank you, I will take that for my d...' Then she stopped and corrected herself to say, 'For my baby'.
"When she shook hands with me I said, 'You nearly slipped up there, you were going to say daughter, weren't you?' She smiled and said, 'What do you mean? We don't know yet'.
"I teased her and said, 'Oh I think you do' - to which, still smiling, she replied, 'We're not telling'.
"I'm certain it's a girl. She wouldn't have said the D-word otherwise. After she said it, she was a little flustered."