There's no problem lying on your stomach in early pregnancy. At this point, your uterus is still nestled behind your pubic bone, so it's totally protected. Later in your pregnancy, sleeping on your stomach just isn't going to be comfortable. You'd be too uncomfortable to want to do it long before you could ever hurt your baby.If you typically sleep on your back, it's safe to continue doing so through the first trimester. But as the uterus gets heavier in the second trimester, it's best to choose another position.When you lie on your back, your uterus presses on the vein that returns blood from your lower body to your heart. Lying on your back for an extended period of time could interfere with the flow of blood and nutrients to the placenta and your developing baby.This is potentially unsafe, particularly if you have a condition like high blood pressure that affects how much oxygen and nutrients the baby is getting. If you have such a condition, your doctor will advise you to sleep on your side.Also, both sex and masturbation are perfectly normal and safe through-out your entire pregnancy, as long as you are not high-risk or any other sort of issues. Sushi is dangerous though, and like alcohol & drugs, should not be consumed at all during pregnancy. Another thing is soft cheeses (including blue cheese) and hot dogs should be avoided as well, lots of women don't know this.