Kate Middleton has recently been forced to pull out of a society wedding amid fears that the Duchess of Cambridge may go into labor during the event, the Daily Mail reports. 

Middleton and husband Prince William are expecting their first child in mid-July, but the Duchess has decided not to risk the 300-mile drive to the big wedding of Thomas Van Straubenzee and the Duke of Northumberland's daughter, Lady Melissa Percy, at Alnwick Castle tomorrow. Middleton is a friend of the Duke of Northumberland's son, Earl George Percy. There will be about 500 guests in attendance, including Chelsy Davy, the ex-girlfriend of Prince Harry.

"The birth may be a few weeks off, but there is still a very slim risk she could go into labor," a royal source told The Sun. "Kate is gutted - as are Tom and Melissa - but she decided not to take any chances."

Last weekend, Middleton attended her last public appearance before giving birth at the Trooping the Colour ceremony with other members of the Royal Family in celebration of the Queen's birthday. At the ceremony, Middleton wore a pink Alexander McQueen coat, teasing the possible sex of the royal baby.

Prince William, Straubenzee's best man, will still be in attendance along with his brother Prince Harry and and girlfriend Cressida Bonas. The groom is a longtime friend of Prince William and Prince Harry, and the brothers attended his bachelor party in London earlier this month.

The wedding service will be held tomorrow at 5 p.m. followed by a reception in the castle's State Rooms and a dinner in the marquee. Lady Melissa's wedding dress will soon after be displayed alongside her sister Katie's in The Coach House at Alnwick Castle.

Middleton's royal baby is expected to bring millions to the British economy.