1 and 2 are way too dark for my taste.
You dont see where her arm is in 1 and her entire body melts into the shadows in 2. A little less darkness would mean you would cut her out of the picture a bit more and make her stand out.
3 is also very dark, but the darkness doesnt affect the overall picture. The water looks very black. I dunno
I guess maternity and darkness arent things I normally put together. They are also not too in focus.
4 is my favourite picture of the set. Nice colours, nice facial expressions. The picture doesnt seem as sharp as it can be, but its still nice. If I were to change something it would be the blue blanket. Seems like the colours are a bit too saturated and the blue jeans + blue blanket are a bit strong
While I like the overall set, I find always having them looking down gets to be a bit depressing. The only one they are not looking down at is #3, where they are looking at each other. I love to see crisp and clear eyes in portraits. I get the mood and pose, but would be nice to have some variety. Seems a bit somber for something that she be happy.
For a first portrait set, they are pretty good. I think you got most poses and backgrounds right (except for the black on black and faces looking down IMO). The technicalities of taking portraits to ensure a great exposure in the camera so you dont have to work too much in photoshop afterwards.