No more boob for my 20mo

I’m pregnant with our second baby. My doctor said I should wean my 20mo from nursing before my second trimester because it can cause early contractions! I’ve read a little from different pages online about this and it seems to be true but I want some first had answers from moms!! Did you have any complications trying to wean your older child off before they were ready?? And how did you wean them!? I’m trying to have her nurse less but she seems more clingy because I’m trying to do it less. She doesn’t nurse as long as she used to but still likes to nurse for comforting purposes if she gets hurt or can’t fall asleep.