Hello!
I have 3 fibroids and had no actual problems during my pregnancy. I really didn't even know they were there, except for the fact that the doctors could see them on the ultrasound and kept mentioning them and stressing me out!
I know in my case, it was very difficult to get an accurate measurement of the baby during the early stages. In fact, they thought my son was measuring about 6 weeks, when I was about 9 weeks pregnant, so my doctor was pretty sure I was going to miscarry. I had to go back for ultrasound after ultrasound every week for the next three weeks, and when they finally got a good shot of my son at around 11 weeks, he was all of a sudden measuring accurately. They think that the position of my fibroids and the baby were making it difficult to get an accurate look, but after a few weeks, my uterus had shifted in order to allow them a better view.
It sounds like your doctor is being extra cautious, which I'm sure is very stressful, but at least you'll have extensive testing to hopefully reassure you that everything is ok. Also, if you're going for a more extensive ultrasound with a perinatologist, hopefully they'll have a better ultrasound machine than your doctor, which may give you a better look at your baby. I know in my case, my doctor sent me to the hospital because their ultrasound machine was more powerful and that was where we finally got a good look at my son (after almost a month of stress!).
Best of luck,
E.