Should i let work know?

Hi all. I am a college lecturer in the UK and we are due to return to in class teaching from September. Ideally i did not want to let work know i was pregnant (only just found out) until 12 week scan due to current risk of early miscarriage and previous loss. However, due to Coronavirus i would potentially be putting myself at risk of harm by not letting them know to complete a risk assessment? I have only just finished my first year as a teacher (full time nurse prior) so not sure whether to speak tp my head of faculty or direct to HR for advice? I am a bit worried as i will be mostly teaching lower level groups of learners who benefit more from face to face teaching and feel it would be doing them a disservice to online teach them. Thanks all x