You can certainly talk to your healthcare providers about your concerns - some issues can be tested for and some can't. But they can talk to you about the likelihood of having another child with the same issues. Every family is different, though. I think it comes down more to how much you want a second child and your resources, emotional, community support, financial, space, etc. to have a second child when you have a first with higher special needs, or to have the possibility of two with special needs.
I'm a therapy provider who works with many families and I have seen many choices: we have a family who is in the middle of adoption procedures to have a second without passing on genetic issues, we have several families who have chosen to have a single child, but the majority of our families have at least two children, and more than 50% of them have had a second child after the first was diagnosed. There are a few families with more than one child with special needs but most have only one child with issues. Some of the children have significant delays and the families still chose to have another child.
I think that even more than looking at the financial and genetic aspect is trying to learn the probability and then talking to your family or seeing a counselor to think through what it would all mean to your family.
Early intervention specialist and parent consultant since 2002.