I'm looking for a reason for my character to have problems conceiving, followed by a difficult pregnancy and subsequent infertility. She had a son in the early 1990s (perhaps around 1993/4) and it took about two years for her to successfully sustain a pregnancy. I imagine her having had a miscarrage or two as well as a tough final pregnancy. The most important part though is that she's unable to have any more children, and I'd prefer it to be that she can't have any more, rather than she could but it would be highly dangerous for her.
I've googled a number of things such as "neonatal problems" "infertility" and "problems conceiving" but the sites I've found have either been hard to understand or unhelpful in determining what the problem would be.