I've never supported abortion. However, I feel I am qualified to answer this question because "the heart of man is deceitful above all things and desperately wicked". I have a human heart, and my mother used to tell me that I would wish I'd never been born. This was an almost constant refrain whenever I did anything that offended her, or made her life miserable. I was an almost constant source of disappointment to my mother. So the reality is that by saying that I would wish I'd never been born, on a very real level, she was saying that she wished I had never been born.
It makes me feel that I want revenge. I not only wish I had never been born, I wish my mother had never been born. She used to call down God's wrath upon my head, and now all I can do is call down God's wrath upon her head as well. I am certain I am damned, and as Christ points out, it would be better for some if they'd never been born.
So my support for abortion only extends to my own mother being aborted. Barring that, I can heap hot coals upon my head and curse my own conception.
However the context of Ecclesiastes is the meaningless of life without God.
I saw the tears of the oppressed—
and they have no comforter;
power was on the side of their oppressors—
and they have no comforter.
2 And I declared that the dead,
who had already died,
are happier than the living,
who are still alive.
3 But better than both
is the one who has never been born,
who has not seen the evil
that is done under the sun.
For you and I and us:
Jeremiah 29:11 "For I know the plans I have for you,” declares the Lord, “plans to prosper you and not to harm you, plans to give you hope and a future."