But he added: "Let's be sincere about that and let us not slip into a double-think where we forget a whole category of children in our own country."
He said the Government had serious decisions to make on abortion and he was troubled that Children's Minister Frances Fitzgerald appeared to show no concern for the unborn.
But Seanad leader Maurice Cummins was strongly critical of the remarks, while Labour's Susan O'Keeffe described them as "disgraceful".
Mr Cummins said he did not think the deaths of 20 children in Connecticut should be linked with the Irish abortion issue.
But Mr Mullen replied that it "shows how casually the Government thinks about unborn children, right now".
It came as the Government announced it is to introduce legislation allowing abortion in limited circumstances.
The laws, supported by regulations, will be within the parameters of Article 40.3.3 of the Constitution as interpreted by the Supreme Court in the X case which held abortion was permissible where there was a real and substantial risk to the life of the mother -- including suicide. But the leaders of the Catholic Church in Ireland called for TDs to be given a free vote on the proposals.