Tina:  This woman is at great risk for depression, and may need grief
counselling now and extra special support postpartum.  I imagine the
baby's birth will be attended with a major mixed bag of emotions for this
lady.  If she becomes depressed, she may or may not need medication.
However, I believe that there is no longer the distinction in psychiatric
diagnoses between depressions which are caused by external causes (used to
be termed "reactive depression") and depressions with no obvious external
precipitators (used to be known as "involutional" depression, and included
major depression both unipolar and bipollar).  As I understand current
thinking, the chemical reactions in the brain involving serotonin are
similar regardless of the cause of the depression.

If she gets depressed, and if she needs medication, there are a number of
anti-depressants, including tricyclics such as amitriptyline,
nortriptyline, imipramine, and a couple of SSRI's such as sertraline,
possibly paroxetine, which present a low risk to her baby.
Hope this helps, Alicia Dermer, MD, IBCLC.