I quit my job some mths back n found out I was pregnant recently.

I got shortlisted for interviews. Should I disclose my pregnancy? If yes, when should I disclose?

1) when discussing job opportunities with recruitment agencies?
2) during interview with the company?
3) when actual offer is made by the company?
4) after signing letter of employment with company?

Any difference to the above if the role is perm or contract?
Or should I even consider contract positions? Thanks.