I think the opinions on this thread have not been what op what's to hear, she's in shock, distraught, in territorial mode and just wants to save her relationship/family (the latter in its current form), she's possibly also hysterically bonding to her partner in the wake of his (essentially) infidelity, so she's stopped engaging.
But I could help but say, just in case she looks on here again, that this has been rattling around in my head as threads do; and I think.its very likely that her partners demand for a break and refusal to try to resolve the issues he raised was a ruse, a pretext, an excuse.
Break up a partnership with a young child and baby on the way over "issues" you refuse to try to resolve, then a woman turns up pregnant with your child a couple of months later, supposedly from a small number of interactions a few weeks before during the break you engineered?
Nah.
I think it's likely he had already involved himself, to some extent, with the OW; and was contemplating leaving for her, the break was a half way house (and of course he didn't therefore want to try to resolve the isdues he blamed), he didn't have the balls to be honest about why he wanted the break (and possibly leave as a next step), then he didn't follow through on leaving as many many cheaters don't for many reasons. Leaving a very bitter, angry,/raging disappointed, cheated feeling (ironically).affair partner in their wake..An affair partner who's often been told the couple is not really ogether.
Also weird the ow would be having unprotected sex with a new partner so quickly, and not get emergency contraception if she thought something had failed ... more like an established "thing" and maybe risk taking pregnancy to try to expedite him leaving, as somr ow do.
I doubt the story op appears to believe us true. I hope she considers, whether she stays or separates ... he could pull.this shit again.