Course they can!
For the last 25 years, there have been literaly thousands of techs every day that do nails all day while being prego.
These guys are exposed to aprx. 130 times more nail stuff than an average client and they have no problems that people who don't wear nails do.
Of course, saying that... You should still follow your Dr's advice and as always... your manufacturers instructions (proper extraction, msds overexposure info, yadayadayada)
toooooooooooodles