Can babies sense a sibling is otw?

My daughter is 21 months old and super super clingy to me since a few months ago (im currently 6 months pregnant). She has been clingy to me all the while as im a SAHM and look after her full time. However, these days she seems to be even more sticky to me. Everything “mama mama”. My mum told me that it is because she knows that a sibling is on the way. Hmm I’m not sure? But possibly!