AnnG06:
**Read the “Address to Large Families” given by Pius XII in 1958 and you may rethink your desire to only have 2 or 3 children and not 18. **
Here is a link:
catholicculture.org/culture/library/view.cfm?recnum=5370
Be warned, you might cry when you read it. I did and I am a man.
We all need a plan to be in constant service to the Lord. Those who have large families (and those who want them but must suffer the constant sorrow of not being able) constantly serve the Lord. Raising children isn’t easy. My question would be, what are the plans of service for those who intend to only have a couple children? Are the plans for only a couple children so that they have time to serve the poor, the sick, the imprisoned or so that they can have a great career, see the world, and not be burdened with the raising of children?
I read it.
I have to admit it paints a rather idealized and unrealistic portrait of large families (and coming from a large family myself, I have some idea of what the reality is

).
Moreover, I am always suspicious when people call for sacrifices that they will never be called upon to make themselves. As a celibate priest it is very easy for a Pope to say married couples should have large families, because he would never be asked to change his own behavior based on that.
But Pius XII had very pragmatic reasons for saying:
All of these precious benefits will be more solid and permanent, more intense and more fruitful if the large family takes the supernatural spirit of the Gospel, which spiritualizes everything and makes it eternal, as its own particular guiding rule and basis. Experience shows that in these cases, God often goes beyond the ordinary gifts of Providence, such as joy and peace, to bestow on it a special call — a vocation to the priesthood, to the religious life, to the highest sanctity.
With good reason, it has often been pointed out that large families have been in the forefront as the cradles of saints. We might cite, among others, the family of St. Louis, the King of France, made up of ten children, that of St. Catherine of Siena who came from a family of twenty-five, St. Robert Bellarmine from a family of twelve, and St. Pius X from a family of ten.
Every vocation is a secret of Providence; but these cases prove that a large number of children does not prevent parents from giving them an outstanding and perfect upbringing; and they show that the number does not work out to the disadvantage of their quality, with regard to either physical or spiritual values.