Wow you're really unfamiliar with how the reproductive systems of women work, aren't you? What do you think? Women get a text reminder they are ovulating? Not to mention, nothing to stop the man from using, you know, a condom! Easy peasy.
<here's a hint. most women have no idea WHEN they are actually ovulating>
It's very unlikely for a woman to conceive based on sex not in her current cycle. Thus, barring good evidence as to when she ovulated she should consider anyone she had sex with during that cycle to be a possible father. Naming one as a father when she knows there are other options is lying.