Do you know this person? Are you able to say with any evidence that the pregnancy is not intentional? Or are you just making an assumption?
In my experience, including approximately ten years as a family law attorney, whenever a couple gets engaged after or at approximately the same time as finding out the female is pregnant, the pregnancy was unplanned.
I'm sure there are exceptions but the likelihood is very rare.
In other words, you don't know these people and you're making an assumption based upon no evidence.
Actually, the timing of their announcement would constitute circumstantial evidence.