I checked the raws and we in for a whirlwind but i think he may find out in the next few chapters idk it is unclear in the raws if he finds out or not. However how the raws left off I assume he found out something. We have a few chapters before we get to that tho! Hope this helps!
Spoilers
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Louis starts having pregnancy cravings (e.g., strawberries), which Maetel sources even though they're out of season! Maetel also notices that Louis is sometimes unsteady on his feet and has mood swings. I think Maetel either finds out or has a strong suspicious that Louis is pregnant within the next two or three chapters.
He's not sure whether it's his or not, because he thinks Louis will just hop into anyone's carriage and sleep with anyone. Which definitely isn't the case; Louis was under the influence of a drug that one night four months ago, and Maetel has drawn the wrong conclusions about Louis' behaviour as a result.
Maetel finds out that it's his baby when he confronts the Duke in later chapters. The Duke confirms that Louis was drugged. He also confirms that the father of the baby was whoever Louis slept with that night four months ago, but isn't certain whether it's Maetel. Maetal knows it was him, and what the Duke says is the missing piece of the puzzle for Maetal to confirm that the baby is indeed his.
Thank you both of you(◍•ᴗ•◍)
Can someone spoil??? When will the prince the thing about pregnancy?