Your wife's milestone birthday is a reason for a celebration. Throw her the ultimate birthday bash so that she's surrounded by her close family members and friends to relish in this special time with her. Think of a creative theme for the party based on your wife's personality, interests and hobbies. For example, if your wife adores classic Hollywood films, incorporate a black and white decor into the party and hire a few celebrity impersonators for entertainment. Or, if your wife enjoys vacationing at the shore in the summer, plan an ocean-themed or seashell-inspired party at a nearby beach house.

If your wife is the low-key type, she may prefer to do something on a smaller scale to celebrate her 40th. Skip the big bash and plan a vacation for just the two of you to a place she's always wanted to go. Surprise her with that trip to Paris or the cruise to Jamaica that she's mentioned she'd like to take. Alternatively, stay within your budget and plan a special one-night vacation. Find a nearby hotel or bed and breakfast with a romantic atmosphere and order room service.

Treat your wife to the gift of relaxation for her 40th birthday and make her feel like royalty. Arrange for a limo service to pick her up and take her to a spa center. Surprise her with the ultimate head-to-toe spa package that includes everything from a body massage to a sugar scrub pedicure and a champagne brunch. Or, have the limo take her straight to her favorite hair salon for a fresh cut, color and styling. Another option is to have the limo take her to a private relaxation class to release any tension she has. Consider an one-on-one tai chi or deep breathing class.

Your wife's birthday would not be complete without any gifts. Consider giving her items a little different than what she normally would expect on a birthday. Nostalgic gifts can bring back fond memories of her childhood. Gift her with a collectible doll that she had when she was young or a box of retro candy that she loved as a little girl. Another option is to give her gifts to let her know what was happening in the world when she was born. For example, you could give her a framed reprint of the front page of a magazine or newspaper that circulated on the day of her birth. Alternatively, present her with 39 small gifts and one large and memorable one -- like a piece of jewelry -- on her special day.