Friend's hubby told me she's cheating

One of my closest friends just had her 3rd baby and she is on mat leave. We work together in an office, and her husband works with us as well, but in a separate part of the building. He told me today that he found out last night she was cheating on him since she was pregnant - he found msgs and pics/videos on her phone between them. I had no idea, and it seems really uncharacteristic of her - she LOVES this guy. They've been married for 2 yrs and together for 11. In fact, I don't think he treats her that great at all - but it's not my business - nor is this information he shared with me!

Should I tell my friend he told me? Or just pretend I don't know? I'd be FUCKING furious if my husband confided in one of MY friends - and I'm not the only one at work who knows both of them that he's told.