Before Diana, royal mothers followed a birth custom of the time for delivery: "Twilight Birth," in which the laboring mother is drugged, and while in and out of consciousness, a doctor used forceps to take the baby out. This is how Queen Elizabeth gave birth to Prince Andrew, and Queen Victoria's drug of choice was even wilder: she used chloroform, and she loved it.
Diana, on the other hand, opted for a more natural birth, even choosing an upright position.