"Pregnant" woman

hee...ok,let me tell you the story.Last tuesday,I was thinking something in MRT on way to work.Then I saw a woman standing near me.I was wondering if I shall give up my seat to her or not cuz' I was not sure if she was pregnant.She has abit big tummy (look like pregnant for 4 months).She looked chubby.Not only that but she wears loose tank top and pants and has line above her boobs.(look like maternity tank top)When it was time for me to alight at commonwealth MRT,then I waved at her and pointed at my empty seat but she looked shocked and shook her head as if I called wrong person.I realised that she was not really pregnant so I walked away quickly and stood in front of window till alighted off!Of course,I was embarrassed.She is more embarrassed? Hard to tell if she is pregnant when she is fat or chubby! hee...I won't approach any clueless pregnant-looking women but I will definitely give up my seat to those who have heavily pregnant as it's very obvious,right?hee...