It is very common that when a pregnant woman is seen, her belly is immediately touched to see if the baby's kicks are felt or simply to see if her belly is hard or not. Actually you should not touch the belly of a pregnant woman without her consent for a very obvious reason: it is disrespectful. People around a pregnant woman should keep up with her at this stage, leaving and respecting the physical space required to feel good.
There may be women who do not mind having their tummy touched during pregnancy, but there may also be other women who feel totally invaded if this happens to them. If you want to touch the belly of a pregnant woman, you will have to wait for her to invite you to do it., or at least give you permission.
It is about physical respect for another person, the same physical respect that you have for any other person. That a woman is pregnant does not allow you to touch her belly just because you are excited that the woman's body is capable of harboring life inside. It does not give you the right to touch a body that is not yours without consent.
There are women who do not like physical contact with other people and can feel very violent if they are touched without their consent. There are also people who, being extroverts, touch others when they speak almost without realizing it, but in any case, it is necessary to know the pregnant woman before asking if you can touch her belly.
From now on, when you see a pregnant woman, do not think that her belly is available to everyone to be touched, because it is her body and she decides.