Answer: I am afraid I do not have a straight forward answer to your question concerning loss of sensation. I know many women have used vibrators for years without loss of sensation, but I have received accounts from a couple women who say they have experienced a decrease in sensitivity. I am not sure the vibrator was the cause in all these cases. There might have been environmental causes like stress or declining health. In other cases they may have come to expect stronger stimulation, as a result of using a vibrator. A vibrator simply works best for some women, and in some cases only a vibrator will provide the necessary simulation to experience orgasm. The Good Vibrations Guide to Sex states, if there is a loss of sensation, sensitivity returns to normal in a short period of time. There is no permanent damage to the clitoris. Keep in mind that some doctors recommend them to their patients.
What is recommended by some is that women not place the vibrator directly against their clitoris. Specifically, do not press it directly and firmly against your clitoral glans. Vibrations should provide the stimulation not pressure. Apply the vibrator to the pubic mound and outer labia, not the clitoris directly. The other option is to place a folded towel or cloth between you and the vibrator, to soften the vibrations, or leave a layer or two of clothing on. All vibrators are not created equal, some may produce weak vibrations and can be placed directly on the vulva. You can also cup your vulva with one hand while holding the vibrator with the other. Do not try to have orgasms quickly, use less stimulation for a longer period of time. Slow buildups and teasing are usually better for more stronger orgasms. I realize if something feels really good, it can be almost impossible to hold back and not go for it, in that case, just do not do so every time.
Continue to explore vibrators, but go slow and do not over do it. If you do get carried away, I'm sure your body will return to normal in a couple days. You can certainly explore using vibrating insertables for vaginal and anal stimulation, while using your fingers on your clitoris.
There are many sex toys that you can try that do not vibrate. Try different dildos and butt plugs. Buy a dildo and harness and explore the masculine or dominate side of your persona. Buy Velcro wrists and ankle cuffs and explore bondage, or get a paddle and explore mild S&M. Go grocery shopping and explore using food during sex. The sky is the limit. Do not forget the basics like full body massage, for exploring pleasure and intimacy. The key is to do things in moderation, and not to rely on the same thing every time. Use a mixture of techniques and scenarios. You should also explore pleasure, try not to see orgasm as the ultimate goal of sex.
We tend to use what works best, so you may like to use a toy if it gives you a lot of pleasure. This is only natural. A sex toy can enhance partnered and solo sex, but it can never replace a partner. Toys cannot hug you back or provide emotional intimacy. They cannot replace a partner in bed. As long as you do not use a toy every time, it should not affect your ability to enjoy other forms of sexual pleasure with your partner.
During a normal and healthy pregnancy there is no need to stop using sex toys, while using common sense. You always want to keep your toys clean to prevent infection, by washing them with antibacterial soap, and rinsing really well. I am not aware that orgasm is harmful, many women experience orgasm during pregnancy. Women use vibrators during their pregnancy as well, with no known ill effects. If you are having fun, so will the baby.
My online poll explores the subject of vibrator use, and the possibility for decreased sensitivity.
A couple medical studies have explored the use of vibrators by men and women.