I’m afraid this is a ‘It depends’ answer for general classes. Unless you’re going to a Pregnancy Yoga class, it is better to play it safe during your first trimester and not attend class. This is especially true for people who’ve done no yoga before. Of course there are plenty of people who do yoga before realising they are pregnant, so please don’t panic if this is you.
I teach in the Viniyoga style which is very accessible and doesn’t generally include many of the poses that are best avoided in pregnancy, eg wheel, bow, headstands. Also we practice in normal (Irish!) temperatures – hot yoga is not recommended during pregnancy, so once you’ve had your first scan you’d be welcome to get in touch about joining my classes.
Every pregnant woman is different and what’s ok for someone else may not be ok for you so I’d want us to have a chat before you joined. I’d want to know if you’ve done any yoga before and your current fitness/health level. We could also decide on a ‘code word’ for modifications you need during class, if you don’t want anyone else to know you’re pregnant yet!