The Desperate Housewives star is already mum to twin girls and she told her Twitter.com fans she was expecting another multiple delivery.
In a post on the site on Sunday, she declared: "Just found out I am pregnant with triplets!!!"
While some fans figured the message was an April Fool, others flocked to congratulate the actress before she finally confessed she was joking.
Cross told her followers, "April Fool's (sic)!!!! Couldn't let that one go for too long !!!!"