Sitting for a prolonged period of time can affect your blood circulation po. If possible po, elevate your feet po while working. Then stand up and stretch every few minutes or so. Pelvic exercises arw important too to prepare you for childbirth and post partum recovery. Here are some exercises po, just pick those that you can do at your workplace :) https://www.tommys.org/pregnancy-information/im-pregnant/exercise-in-pregnancy/5-easy-office-exercises-do-when-youre-pregnant
Yes mommy it's not always safe po to sit for a longer period. But for working moms like you, it is advised po na umupo ng matuwid, at tayo tayo din minsan. Ang effect po kasi kapag matagal nakaupo is yung daloy po ng dugo hindi maayos tsaka po yung oxygen po na kelangan ni baby.