Mosquito repellent

How much deet should be in mosquito repellent? What's safe for pregnant women? My doctor said to get bug spray with deet and I didn't realize there were different percentages. I got some with 7% but wondering if that's too low? The next percentages I saw was 15 and 25%. I plan to call my doc tomorrow but thought I'd ask on here since its after hours there and maybe someone knows!