I think I can actually give you TWO perspectives!
DH & I are both only children. We are two types:
I was a "planned" only child. My mother and father were both the middle of 3 children and thought is was the worst thing in the world a parent could do to a child (their words, not mine
: ). Though they divorced when I was 3, they had never intended to get pg again. Both remarried and did not have children with their 2nds.
DH was an only by "default". He was to be the first of at least 2. However, after he was born, my ILs endured 2 m/c and then my MIL had an emergency hysterctomy due to uncontrolled bleeding after the 2nd m/c. My FIL was considered "too old" to adopt at the time (almost 40! can you believe it!
), so ILs just "resigned" themselves to one.
We are very different, but similar. My mother was a single mom most of my life (her 2nd marriage didn't last any longer than the 1st
) I grew up with modest lifestyle ~ as in my parents weren't rich and didn't have a lot of money to throw around. Though I was well taken care of and a bit spoiled in that when there is only one child, even a little bit of money goes pretty far. DH was doted upon. Given a car at 16, designer clothing, expensive gifts. However, we are both well grounded. Our parents instilled values in us (though DH wouldn't buy generic food at the grocery store till we were married!
I think the things that are advantages are the same things that are disadvantages about being "onlies". Like, since we were onlies, we received a lot of one on one attention ~ but it also meant that we received a lot of attention, we couldn't get away with anything, no one to blame stuff on. We never had to share, but we never had to learn to share. There was no sibling rivalry, but there was no comradery. As an adult I am the only one who will make any decisions for my parents (both are now single), which makes things very unilateral ~ but is a large weight to carry. You can expand the list on forever...
I think "bad" onlies come from poor parenting, not from being an only. I know plenty of "youngest" or "oldest" or "middles" that are snobs, spoiled, self-centered, or any of the list of things that can become labels for onlies. Like how people assume that homeschoolers have no social skills. It depends on how you expose them to the world. DH & I were both very active in church & sports, our parents made sure that we could take care of ourselves, and I don't really think that either of our parents were particularly "doting".
HTH! No matter what, I think that you are being VERY wise to consider what having another child will do to your family. I had 4 m/c before DS. We were trying to decide whether we were going to even try anymore when we found out we were pregnant w/DD!
Just out of curiosity ~ is it just the "bad" pregnancy that is making you think that you don't want to have any more children? We would like to have more children ~ we just don't want to get pg again (not only did I have 4 m/c, but had a very difficult pg & traumatic birth w/DD). You might consider adoption or foster parenting to expand your family...