Do All Women's Vaginas Pulse During Orgasm?

Dear Dr. Betty,
My wife is a big fan of the Hitachi Magic Wand (thanks to you). After a warm up period with the wand, I am lucky to be able to pleasure her with a large dildo. (How I wish I was that big!) This is a guaranteed orgasm for her - never fails. I really love this ritual as it allows me to enjoy her visually - there is nothing quite so powerful as watching a woman you love enjoying an orgasm. She always takes the dildo out when she reaches orgasm and her vagina pulses repeatedly. It is truly the most powerful thing I have ever seen and I can't get enough of it.