We really don't... except perhaps for the Jesus affair, but it's quite likely he was dead and stayed dead, as people tend to.
Flavius Josephus writes in
Vita:
Once more, when I was sent by Titus Caesar with Cerealius and a thousand horse to a village called Tekoa, to prospect whether it was a suitable place for an entrenched camp, and on my return saw many prisoners who had been crucified, and recognized three of my acquaintances among them, I was cut to the heart and came and told Titus with tears what I had seen. He gave orders immediately that they should be taken down and receive the most careful treatment. Two of them died in the physicians’ hands; the third survived.
In many things, getting taken down from the cross while alive included, 'who you know' is of utmost importance.
Back to the New Testament-era Jerusalem setting: the Roman governor was supposed to come up from Caesarea for Jewish holy days and hold his assizes there, among other things. Hence it was more likely than not that there were people hanging on the crosses, getting burned, etc. during the festivities in question.
Pregnant women weren't crucified by Roman authorities. It just wasn't the done thing.
If one wants to put them on the cross anyway, sticking to fantasy settings is -- in my humble opinion -- the best thing to do.