Short answer
Material circumstances that could reasonably affect married life should be disclosed in an appropriate and respectful manner.
Islamic Guidance
What Islam teaches
Marriage requires honesty and trust. Concealing important information that would reasonably influence the other person's decision can cause serious harm.
Practical Guidance
What you can consider
Discuss significant circumstances privately and respectfully, focusing on facts rather than labels. When a matter is complex, professional or qualified advice may be appropriate.
Sources
Qur'an 4:19; Qur'an 5:1.