Hi Maria, Congratulations!!
As far as stretch marks go, I say fight the good fight if you don't want them. I was sure I was going to get them because my mom got them and I got quite a few when I sprouted boobs and hips at age 11, almost overnight. My brothers got them from growth spurts too.
But I did some research and found that slower weight gain, hydration, moisturizing your skin, and a balanced diet with natural fats from nuts, seeds and fish oil can make a big difference. So why not try it???
I've always been a post shower body lotion type, so I kept that up and put more on my belly, hips, boobs, back, butt and arms. Nothing fancy, just Aveeno body lotion. I eat lots of nuts and seeds already and I take fish oil capsules b/c my mom died of cancer. I also eat quite a bit of fish but have cut back during my pregnancy. I bring a 32oz Nalgene water bottle with me where ever I go...I did this before I was pregnant too. I drink 2-3 of them a day, more in the summer.
Oh, and I went out in the sun in a bikini and let my bump tan, something they suggest you avoid if you don't want stretch marks. We're beach people and it made me happy that I didn't have to give up enjoying the sun and swimming in the waves. I did it later in the day (after 2pm) and lathered up the SPF 30.
I'm 38+ weeks now and don't have them yet. Yes, I could still get them but my point here is that every body and pregnancy is different so why not take good care of yourself and take steps to avoid them.
BTW I had a huge growth spurt at 7-8 months and gained a quick 16lbs in about 5 weeks. That was when I thought I was doomed for sure. I re-applied lotion when my skin felt itchy or tight, and my body & skin adapted. Thankfully the gain slowed down after that.
I'll keep you posted if any appear...but I'm still hoping they don't!!
Good luck!!
Steph