The singer will not perform on the first of her scheduled dates in Antwerp on her Mrs Carter Show World Tour, after doctors ordered her to rest, AP reports.
She is due to perform at the Sportpaleis again on Wednesday, but a statement issued by her publicist says she is "awaiting word from her doctors before making a decision".
The news comes just a day after it was claimed that Beyonce and husband Jay-Z were expecting another baby.
US website MediaTakeOut claimed that the news has been confirmed to them by her people, revealing that she is two months pregnant.
The New York Post also said that "multiple sources" supported the claims following Bey's appearance at the Met Ball last week.