Saint Luke puts it so perfectly

Fighting against something doesn’t achieve anything; it is fighting for a cause that is worthwhile. A doctor fights for life, he cannot change sides. The very small children, who are still in the womb, are as alive as the others. The only difference is that they are much younger. The serious degree of a homicide cannot be measured in terms of how much the victim weighs.

The most illustrious physician of all time (Saint Luke) has given us an idea of this marvel that is early childhood, in just a few words. Go back to the story of the Visitation: How old was the little prophet who leapt inside Elizabeth at the approach of Mary carrying Our Lord? He was 6 months old. Saint Luke noted the detail.

And how old was Jesus? The Gospel simply says that after the Annunciation, the Virgin rushed to the assistance of her cousin: "Maria festinavit." As such a journey cannot have taken very long, Jesus’ body was unbelievably young at the time of the visit. Saint Luke puts it so perfectly that we dare not add anything to it.

Dr. Jerome Lejeune

Taken from an interview with the French geneticist, who discovered the cause of Down syndrome and was a fervent disciple of Mary, published in the magazine Le Sourire de Marie (Mary’s Smile).