Drinkin/drugs and pregnancy.. most important stage

This is a sincere question and believe me I do not condone it whatsoever (based on the title)...

I'm not sure how to ask this question where it makes sense because clearly the answer is never but my question is...

In what stage of pregnancy does drinking or doing drugs truly affect all aspects of children's development..

Hear me out real quick

There are millions of people who don't even know they're pregnant and went out for a night of drinking or drugs or whatever and find out and then stop.... does that affect the baby in some ways

Or do you think it affects the baby more so later during pregnancy because that is when they say the baby's completely developing their brain etc...

I know I'm going to get a lot of backlash so let me again say I don't condone it whatsoever but do you think the beginning stages of pregnancy are more important.... or the middle... or the end I get every stage of pregnancy is very serious but in which stage do you think it's really really could cause harm

Ps. Im not pregnant..

Just popped in my head because the show intervention 🤦‍♀️