i wish i knew what to say, but honestly there's not much we can do as a third person in that situation. of course its unfair, but all we can do is spread awareness and urge them subtly.
shit, i begged my dad to stop smoking around us when i was little and he put in little to no effort to change that. im not saying its okay- but again. what's done is done. you just have to figure it out after that. and sometimes its their own struggle as well, you don't always know the background. and like i said, if they're going through with the pregnancy then be ready to deal with the consequences.
what i will say is that the poc girl in my school that said she would give up the baby if they came out a certain way pissed me the fuck off. and she further thought it was okay because she had a disabled cousin. that was disgusting. mocking the results as if it wasn't the product of your own actions, is disgusting, acting as if that's not your issue to deal with is a terrible way of thinking.