oh mandy! there is no understanding this kind of thing. so sorry for you, your young niece and her freshly lost baby boy
we know nothing of ob/gyn reasoning for physical reasons but you sure are correct that her psychological trauma might be more than her ob/gyn could fathom.
sadly this type of loss could be used to bring attention to importance of mental health support for expectant mothers who face sudden fetal death or miscarriage. again we don't have links or info but wish that more could be done.
so very sorry mandyfins. we never understand why such young ones never get breath on this planet. deepest sympathies to you and yours.