Moms are a constant source of support and warmth.

Now, while that is completely true, contribution of mothers goes way beyond these things. It can be life-changing in very quantifiable manner. 

Twitter user Prashant Singh used the occasion of Mothers' Day this year, to explain this with an interesting anecdote:

He and many of his college friends, met for a reunion decades after graduating. Some even had kids who were now going to university. 

Anyhow, as the evening progressed, the effect of alcohol started manifesting itself in the form of philosophical discussions. Who went on to do what? Who is happy? Who is not? Questions like that.

While talking, the group found a theme for their discussion. Unpredictability. The conventional notions of A leads to success and B does not, were thrown out of the window.

So they sat down to figure out what that one factor which made people successful in their personal and professional lives was. 

Unable to come to a solid conclusion, they decided to do what one does in these situations: Make an Excel sheet. They went all the way through and zeroed down the list to 8 people, who had achieved the most in life.

It was relatively easier now. They just had to find the common factor among these 8 people. Which, they figured, was working moms.

Yes, all these people were raised by mothers who were working when they were growing up.

After this, it was easier to come up with factors that may have contributed to these people's success and prosperity.

Prashant concluded the thread by saying that we tend to undermine/ignore women's contribution to the society and data research might throw more light on the subject.

In that context, here is a Harvard study (also shared by him), which shows that children of working moms turn out be as happy and successful and those raised by mothers staying at home. Which should help in alleviating the parenting guilt women often carry.

So, in case anyone has the audacity to ask for 'proof' to show what women have done, you can refer them to this thread.