Opinions needed : long post

I need to purchase my bridesmaid dress for my brothers wedding in early November . I just have no idea what size to get . I’m currently pregnant and due next month . I’ve only gained 5 pounds this pregnancy . But I’m curious as to what you ladies suggest . Im comparing it to the dress I got for my sisters wedding last October because it’s similar in style . My measurements don’t match on their size guide some are a bigger size dress . I’m hoping to avoid alterations if I can due to money. But because of the flowy bottom I feel I should stick with the correct measurements for my upper half . I was worried about the zipper on the back but both dresses have the same type of zipper .

Also not expecting to lose a lot of weight after delivery . So I feel I’ll be around the same weight as I was with my sisters wedding

This is the one I wore to my sisters wedding

Size 1x 16-18

Bust : 43-45

Waist: 36-38

Hips:46-48

My hips and waist measure bigger but according to my sister and the lady I took it to to get altered said the size was perfect for me .

This is the dress I need for my sister in law

Also 1x size 18-20

Bust: 45-47

Waist: 38-40

Hips: 48-50

Or

Xxl size 16

Bust:42-44 ( my size exactly) straps adjust if needed

Waist : 35-37

Hips:45-47

Other bridesmaids have said this dress is pretty accurate if not perfect in size .

Thank you to anyone who takes the time to read and offer some suggestions .