You’re fine to wear aligners if you’re pregnant, they’ll cause no further damage although you may find that your gums are more sensitive, so you might feel in more discomfort than you normally would. Don’t worry, as they should settle down as normal after a couple of days once you switch to each new set of aligners.
SnapCorrect even mentions how aligners can be beneficial if you’re suffering from morning sickness, as they can protect your tooth enamel from stomach acid. Just make sure to properly rinse your aligners if you are sick while wearing them so that acid doesn’t remain on them and potentially cause damage.