It's fine to 'poke' the outside of the baby bump. In fact it's the first 'game' you can play with your little one. :)
Is it okay to poke my pregnant belly?
Sure… if that’s what you want to do. It might seem weird at first, since baby is so small and still developing. But your baby is incredibly well cushioned in there. Remember, she’s floating in a sac of amniotic fluid, which is surrounded by a thick, muscular organ (your uterus). On top of that is your skin and belly fat (more cushioning!).
Of course, just because it won’t hurt baby, doesn’t mean she can’t feel you poking — in fact, baby will probably feel you move and poke before you can start to feel her, which is usually at around 18 to 20 weeks. And when baby’s big enough, she might even poke back!
Kelly Kasper, MD, ob-gyn and associate clinical professor at the Indiana University School of Medicine, in "Is It Safe To Poke My Belly?" for The Bump
A baby in the womb is quite well-protected, it takes a hard fall - the kind which injures mum - to injure the baby:
In the first trimester, a thick, muscular uterus and an even more protective pelvic bone shield your baby, so it is nearly impossible to injure her if you trip and fall. By the fifth month, however, your uterus grows beyond the protective shell of your pelvic bone. While the chances of injury from a simple fall are still very unlikely, many pregnancy worries stem from these changes in your body.
... There is no need to worry unduly about minor falls. Your baby is well protected by the natural shock absorbers of your abdominal muscles, uterine muscles, fetal membranes and the amniotic fluid, all of which cushion any outside blows. It would take an accident that seriously injures mommy to have even a remote chance of injuring baby.
Growing Concerns, Ask Dr Sears