For me personally, I began to gain weight around 8 weeks. Pre-pregnancy I am 5'2" and was 108 pounds. I am currently 16 weeks and my lower abdomen area is beginning to poke out somewhat. It is below the belly button, that is where your uterus and baby are in the beginning and it gradually moves upward. I gained nearly 10 pounds between 8 and 16 weeks and for the most part it wasn't all in one specific area.
I have 3 kids, the latest is 5 months, Isabella Julia, Anna is 4 1/2, and Anthony is 11.....
Im 5'1 and 95 pounds. Perrsonally, all the weight i gained went to my boobs and belly.... It started at the lower belly (pelvic area) and slowly bulged out and up... i gained 30 with Anthony, 20 with Anna and 15 with Isabella, she is my last.
I am 11 weeks and just started to notice some growth changes last week. I am normally flat stomached so it is easy to see on me, but where it is definitely happening is the pelvis area, it now sticks out and looks really strange. I havent actually put any weight on, in fact I have lost a little but I can still see the growth.