I'm so very sorry for your friend's loss. I can't even imagine the heartbreak and pain. 💔
My wife and I thankfully never experienced this. A friend of mine did, though. Unfortunately, they didn't live near us so I had to watch from afar...
How did you get through it?
I really don't know how they did, frankly. Both a deeply religious, and they certainly drew some strength from their faith. They leaned on family and friends - sometimes a lot more than they ever expected to, and sometimes for seemingly simple things like, "Oh, we need milk."
Were you able to have children thereafter, and if so were the births difficult? (of course, her biggest concern/fear)
My friend and his wife (well, they're both my friend,really) were in fact able to have two beautiful, wonderful girls. The girls knew about their "brother in heaven" from the beginning. Both pregnancies were thoroughly normal, although of course they were terrified each time.
Everybody is different, of course. From what I understand a whole lot of the answer here depends on why. This is a conversation your friend can have with her doctor once she's ready.
And from myself....How can I be there for her without being too intrusive?
My opinion? Be intrusive, at least sometimes. Cook dinner. Take their dirty laundry back to your house and bring it back the next day. Arrange for somebody to mow their lawn. They're reeling, and our society teaches us that whenever somebody asks, "What can I do to help" we usually don't say. That doesn't mean you should always be intrusive, of course. Ask what they need/want and listen to what they say - and how they say it. But if they tell you some form of "nothing" pretty consistently, find something to help with.
Aside from that, be a rock for her. Give her - and her husband! - your shoulder whenever it's needed. Hold her hand while she talks through her feelings. Offer to take her - or at least go with her - to any doctor's appointments. And never judge her, no matter how tempting it may be at times. We all grieve differently; there's no right or wrong way. Let her grieve her way, and support her as best as you can through it.
Good luck. Again, I'm so sorry your friend is having to go through this. 😥