I feel really bad for her if she really has had two miscarriages. But this post, written when she was pregnant with Lachlan, implies she has never had one, at least at that point:
http://thismamalife.com/worrying-about-miscarriage/
She wouldn't write about having no reason to worry about having a miscarriage if she'd already had one - trust me, once you've had one you spend your subsequent pregnancies absolutely terrified.
Something doesn't add up. I know she is an Instagram addict but surely she would draw the line there when it comes to getting engagement.