Which one is correct?

[MAJSH]

Since our marriage in 2000, we never had a child other than this pregnancy. Since our marriage in 2000, we don't have a child before this pregnancy.

[freezeframe]

Since our marriage in 2000, we never had a child other than this pregnancy.
Since our marriage in 2000, we don't have a child before this pregnancy.

Typically if someone asks "do you have any children" and you're pregnant, you say "I'm expecting". We don't talk about pregnancy as having a child.

Also the "since our marriage" part makes the sentence confusing. Did you have children before your marriage in 2000?

How about:

We got married in 2000 and now we're expecting our first child.