1.04 no mods
My character is a duchess and my husband (matrilinial marriage) just died. Right after I got the message I was pregnant and I also got the penalty for being pregnant without a husband. It was at most a few weeks after my husbands death so it would definitely be plausible that my husband was the father but I was not sure at this time if my character had found someone else to warm her bed right after the funeral.
When the son is born he is a legal heir showing my dead husband as the father and is of my dynasty. One strange thing is that he has the fathers last name & culture and not mine like the rest of my children - this looks like a bug.
The pregnant without a husband event is probably WAD, but maybe it should not happen if you were married until just recently?
I also remarried while still being pregnant. This got me a positive relationship bonus for spouse view on pregnant from my new husband but it was definitely not his child so would make more sense if it was negative - also looks like a bug.
There was no negative AI modifiers for accepting a matrilineal marriage with my pregnant duchess in her late 40:s, WAD?
Okay, I can confirm the event ("unmarried pregancy") occurs - shouldn't occur, but this may be a case of "not worth the trouble" to catch all exceptions.
Likewise, for the remarrying while pregnant - it's pretty rare, and the fix might be rather involved.
I can't confirm the "husband's last name", though. My (legitimate, as he should be, proper father &c) son properly shows the name&dynasty of the (matrilineal marriage) mother.
With regards to the negative AI modifier - what, specifically, would you expect the negative modifier for that you are not getting? age? pregnancy? matrilineal marriage?