The baby isn’t causing the blues in the first place. It is commenly known as the baby blues or now is refered to Post Pardom Depression. It has to do with the hormones and chemicals in a womans brain and body up to a year after giving birth. Also it is considered a clinical issue that should be addressed by a medical professional.
If you know some one that has the baby blues, you might want to be encouraging and give that person a little help. Give them space to pull their selves together and to attend any appointments related to resolving the depression.