When do you have your evening bolus and meal? It's possible your blood sugar is still rising as you go to bed, though hopefully the libre will show when the spike occurs.
Also, bear in mind that the libre is not always accurate - might have been worth doing an old fashioned finger prick test when you got the 12.8.
Congrats on the pregnancy. Remember that T1s have been successfully having babies for decades (I'm 57 and my mother was T1 when she had me) and been blissfully ignorant of the spikes you are experiencing because cgms and even glucometers weren't available at the time. And I feel for you on the hypos. I lost hypo awareness during both my T1 pregnancies due to keeping my blood sugars low, and ended up having to have friends watch me when I was alone with my toddler during my second pregnancy, I just wasn't safe on my own. I would have killed to have a cgm then, but this was more than 20 years ago so cgms just weren't available yet.
Have you considered investing in a miaomiao transmitter plus xdrip app so that you can get your libre to generate hypo alarms? (It should also make the device more accurate.)
Good luck.