The two American singers appear to have put their differences behind them.
She tells MTV News: "My assistant came in the room when it happened and she’s like, ‘Britney had a boy!’ and I was like, ‘Oh my gosh!’
"I don’t know where I was for a while when she was pregnant but it really kicked in at that point. It’s like: ‘Wow, she had a baby! That’s crazy!’
"I’m overjoyed and thrilled for her. It’s such an exciting time in her life and I just wish her the best."
Aguilera also revealed that she has already bought a gift for the baby boy.