Telling the ex.

So, my significant other and I are expecting a baby boy in March. He’s just barely come around and accepted that it’s happening.

But his ex has not been the most sane human. He has a 4 year old daughter with her. We’ve just barely gotten things in order with a schedule so that his ex felt like we were helping out more. Don’t get me wrong, we’ve done whatever we could for his daughter. We spend 3 days out of the week with her.

His ex has just been very unpredictable in the past with certain situations. I’m just wondering what the best way to tell her would be? I know no matter what, it’s going to be a hard and dramatic conversation. But I don’t want my significant other to feel like he’s going to ruin what’s been set in place, once she finds out.