The base rate is about 1/160 to 1/200 births.

According to this meta-analysis http://www.bmj.com/content/350/bmj.h3080 the chance of a second stillbirth given a history of stillbirth is about 2.5% or 1/40. This is a lot higher than the base of ~1/200 but it is still pretty unlikely.

Yep. This is the information needed.

Starting from here, since all known predictable causes were ruled out (presumably the more likely repeat failures), I think the probability is somewhere between 1/40 and 1/160.

Maybe you could get base rate variation based on age. And country.

The cooccurrence rate looks like good news to me. Or at least good news if you want to try again. I don't know that the difference between 0.5% and 2.5% would even register in my brain. If someone had told me that the base rate was 2.5%, it wouldn't deter me from wanting a child.

I've done some of my family tree. The sad thing about looking back at cemetery records is how many times you see children under 1 and 2 dying just 100, 150 years ago.