What are the risks of untreated postpartum depression?

Oftentimes severe: Without treatment, the worst case scenario -- harm to either self or the baby, or both; inability to function, post-partum psychosis, with delusion, and/or hallucination. It's better to get treated right away for your own and baby's sake.

Chronic depression: With treatment, there is a very positive prognosis for complete recovery. The risks of not getting treatment are continuing to experience depression, lack of joy and negative effects for children & relationships. See my soon to be released book about positive transformation following postpartum depression, "happy endings, new beginnings: navigating postpartum disorders" ( see amazon new releases).

Many: Colleagues have offered excellent answers. I will add this: untreated post partum depression can interfere with your bond to your baby, affecting you both for a long time. This is an upsetting prospect, but as others have mentioned, the treatment for PPD is usually very effective. Best to address it as soon as possible, even pre-birth if there is reason to worry you are at risk.