Kate Middleton reveals second baby is due in mid-to-late April

LONDON, March 18 (UPI) -- Kate Middleton revealed her second baby's approximate due date Tuesday.

The 33-year-old Duchess of Cambridge is said to have announced the news during an appearance at the Brookhill Children's Centre in Woolwich.

"I told her she is beautiful and that she's got a tiny little bump," volunteer Christie Osborne subsequently told reporters. "I asked when her baby is due and she said mid-to-end of April."

Middleton and husband Prince William are already parents to a 20-month-old son, Prince George of Cambridge. The couple married in April 2011, and announced they are expecting their second child in September 2014.

Middleton and her growing baby bump were spotted at Turner Contemporary Art Gallery and on the set of ITV series Downton Abbey last week. The duchess' royal parents-in-law, Prince Charles and Camilla Parker Bowles, Duchess of Cornwall, arrived in the U.S. for a four-day visit Tuesday.