As long as you don't have a high risk pregnancy, you can have sex safely throughout the entire pregnancy, and can use toys without concern. You will want to be extra careful about the toys being sterilized since you don't want to introduce bacteria (and get a bacterial/yeast infection). You also want to be very careful that you're not bumping your cervix, and I would avoid it once you've started to dilate.
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I masturbated all throughout my pregnancies, but only used a vibrator and some other toys during my last. Everything about my pregnancy was normal, and no amount of sex, orgasms, or toy use caused early labor (my daughter was 10 days overdue!). As long as you're being smart with the materials you're using, and you aren't going crazy with thrusting, etc. I don't see a reason why you would need to stop. If you're concerned about it, speaking with your doctor would be a great idea since they know your specific case, but as a general rule, if your pregnancy is healthy, enjoy!