16w pregnant. start sleeping on my left side at night but wake up on my back. when i'm aware, i change positions but sometimes i'm sound asleep. harm?

Not to fret.: You are only 16 weeks pregnant -so i wouldn't fret too much about pressure against the aorta. It is great that you are already training yourself this way.

No: Absolutely not. This happens all the time. Also, you dont' have to worry about this until later in the pregnancy, like after 28-30 weeks. Just do your best when you get to that point in pregnancy, to lay on your left side. But definitely no harm to baby if you wake up on your back.

No harm: Unless you have other medical problems, how you sleep during pregnancy is up to you. Women in very late pregnancy, however, rarely sleep on their stomachs. The fetus usually does not mind how you sleep.