How bout them drugs with pregnancy?

Okay I've recently asked a question but didn't really put enough detail in it, but anyway, I've heard from several sources that doing an occasional drug before the four months in pregnancy is less likely to harm the baby,(? just because the brain in the fetus isn't developing yet?) I'm not addicted to any drugs, and don't regularly use them i was just wondering if it would be ok to use them recreational once or twice before four months, I've been researching some and would like to find out some other things about it. on my other question i also recommended that people who just wanna put their opinion on there don't. I want real information, I'm truly curious and i don't need people telling me how shallow minded they are because they don't know any real information about any thing.