Photographer Lucy Hilmer has been taking a nude self portrait on her birthday every year for the past forty years, and has recently documented the results online.

Birthday traditions are - of course - highly personal. From making your friends scream when you cut into your cake (it's bad luck to hear the knife touch the plate apparently) to wearing the same outfit year in, year out, there's usually something we all like to do on our special day.

But Lucy Hilmer's 40-year-long project, Birthday Suits, is rather different. Every year she takes a picture of herself wearing a white pair of underpants, socks and shoes in an intimate, but honest way to track the changing of her body, as well as the journey of her life.

Woman takes a nude self-portrait on her birthday for 40 years