Well, blood pressure is one thing that can usually be dealt with, yes, you'll have to be on bed rest for a LONG time possibly, and maybe even take meds during your pregnancy, but you have to decide what's more important to you. I was on bed rest for months with 2 of mine, and yes it was VERY difficult, especially when I had a 1yr old and a 2yr old while on bed rest for 3 1/2 mos, but we survived, we got help from friends, and everything turned out great, now I have my precious angel. But, that's not the right choice for some people.
Now, I REALLY have to laugh at the child wanting a sibling thing. #1, don't most kids? #2, My oldest wants us to have either 14 kids or 62 kids, and he tells people that all of the time. Am I going to do that just because he wants that? HECK no! I'm satisfied with my 4. My youngest is our only baby girl with 3 big brothers, I know she'll be the outcast, and I KNOW she'll want a baby sister (maybe brother, but definitely a younger sibling of some sort). It has to stop somewhere at some point. If you just want her to have a playmate during the summer, get her in a play group, join a church and let her make friends there, put her in a mother's morning out program or 1/2 day daycare so she'll have some social interaction.
You decide what YOU want aside from what your child wants. If you decide more children is for YOU, then talk to your Dr if you think you can handle bed rest. If it's not worth the stress and trouble, don't do it. Also, 3 kids (especially 4) can be VERY stressful and raise your blood pressure all on it's own, so think about that too.
Good Luck!
K.
Stay at home mom of 4