Love for those society considers "useless" or even a bother led St Teresa of Calcutta to a courageous defence of the unborn, said Cardinal Pietro Parolin.

Like prophets and saints before her, Mother Teresa would not "kneel down before anyone but the Almighty" and would not bow before "the fashions or idols of the moment," said Cardinal Parolin, Vatican secretary of state.

On the 19th anniversary of Mother Teresa's death, on September 5 -- her feast day -- the cardinal presided over a Mass in St Peter's Square to give thanks for the canonisation of the founder of the Missionaries of Charity.