It depends .. would you do that for your friends or family? .. Are you generous with your friends when you need to give away gifts and things? Would you be thrilled to buy stuff for a friend's 4th baby shower? It is always give and take, and you know if you are balancing that, otherwise you may slowly end up loosing the support, you have. The kids do not need any fancy things .. it is "US", the parents, who need the beautiful crib and things that go along with it. I have three kids (twins and an older brother, just 18 months apart). I had only one crib. The younger ones can sleep on floor for at least next 6 months, until they are ready to roll, or the older one can sleep in a nice cozy sleeping bag on the floor and the younger one in the crib (if you are afraid that older kids can run over the young one). It is tough financially to have three kids but I look at it is -- it is your choice (or our choice in my case to have 2nd or 3rd), and I would not ask people to help me support my own child. My friends did give me things, and if I had any friend who would not be using her stuff for a while, I borrowed. If anyone did ask me, I asked them to give Diapers as you need lots of them with three kids.
I have two friends with second babies .. and like I said Give and Take .. definitely all in our friends' circle want to throw shower for one, but we are not thrilled to throw the shower for the second one, as she has always been too calculative. Strangely, the one for whom we all would like to throw, does not care or say one time.. but the other one gave us the hint that she would like one again.
So you should judge yourself and you would know in your heart if you should ask people or not. I understand other people's opinion that each child is special .. but the first shower is for parents .. the baby does not know or care who gave what to him/her. The purpose of the baby shower was to help young parents meet the need, and get ready for the transition to be a family -- it was a major change in life to go from couple to family. But once you have one baby .. you should know what you need and should be able to support yourself. I have friends who have 4 or 5 kids ... but would I throw showers for their 5th one .. No .. Will I love the fifth child as much as the first one, and give them B'day gifts (Yes .. most definitely). You can get a lot of cheap stuff if you buy second hand from consignment shops, and like I said "The baby does not care for new or old".
Have a healthy and wonderful pregnancy .. it is an amazing experience to feel the baby inside you.