Would you trust them without muzzles?

My boyfriend and I's dogs got along fine for more than a year. Then suddenly out of nowhere, his dog started randomly biting mine. First time it happened there was a kid screaming outside and my dog was just laying on the couch, his dog ran over and bit her. After that a few days later she bit her again, but it turned into a really bad fight. My boyfriend got his hands tore up pretty good. From there it got worse and worse. We had more than six fights in one month, they'd just see each other and lose it, every single time the dogs got tore open and so did we. So we started keeping them sperated, rotating them in another room and with us.

Months go by like that, and we decided to get muzzles. At first they were both very anxious and they tried to fight but we pulled them apart and told them no, I even rolled my dog onto her back. (I don't believe in "dominating" her, but it is a more vulnerable position. She got the picture.)

So now it's been four months without a single fight. We've had them together for days and they still don't LIKE each other, but they tolerate one another. They've started to go at it only twice, once because there were dogs fighting on TV, and another time because of fireworks from the fourth.

We even had them out once without muzzles but he kept his dog on the bed and I kept mine on the sofa with me.

We lost his dog's muzzle, I can't find it anywhere.

I'm also eight months pregnant, I don't want to risk my baby getting hurt breaking up a dog fight.

So my question at this point is, do you think it is safe to trust them together again yet, or just wait and keep them separated until we find her muzzle?