Dear Claire:

What he is talking about is that John the Baptist was sanctified in his mother's womb, filled with the Holy Spirit at the sound of Mary's voice.

Thus, while John the Baptist was conceived with original sin, it was removed from him before birth. John the Baptist was born without original sin.

Mary was "conceived" without original sin; John the baptist was conceived in original sin, but "born" without it. This is a big difference.

The Catholic Encyclopedia explains:

Now during the sixth month, the Annunciation had taken place, and, as Mary had heard from the angel the fact of her cousin's conceiving, she went "with haste" to congratulate her. "And it came to pass, that when Elizabeth heard the salutation of Mary, the infant" -- filled, like the mother, with the Holy Ghost -- "leaped for joy in her womb", as if to acknowledge the presence of his Lord. Then was accomplished the prophetic utterance of the angel that the child should "be filled with the Holy Ghost even from his mother's womb". Now as the presence of any sin whatever is incompatible with the indwelling of the Holy Ghost in the soul, it follows that at this moment John was cleansed from the stain of original sin.

Pope Innocent III (1208 AD, DS 790) wrote: “Iohannemque Baptistam ab eo missum esse sanctum et iustum et in utero matris suae Spiritu Sancto repletum” (“and John the Baptist had been sent from Him [God] holy and righteous and filled with the Holy Spirit in the womb of his own mother”).

As one person observed, "It is interesting to note that the Nativity of St. John the Baptist on June 24 is an important celebration on the Church calendar. The only births celebrated by the Church are that of Christ, the Mother of God, and St. John the Baptist. Although no dogmatic pronouncements have been made at Ecumenical Councils or through infallible statements of the Holy Father, it would seem that the Church Tradition is making a statement on the holiness of St. John the Baptist from his birth."

It is church teaching that John the Baptist was cleansed of all stain of original sin and filled with the Spirit in the womb. He was thus born without sin.

As to whether John the Baptist lived his life without personal sin, as far as I know, the Church has not ruled.  There are some who say the Church does teach that he was sinless, but I have not found that. But, from what we do know about the Baptist, it would appear that he did live without personal sin.

We know for sure that Mary lived without sin because she was preserved from original sin altogether, which means that she was free from concupiscence.

John the Baptist was not baptized in his mother's womb in the normal sense, of course. But was was sanctified and filled with the Holy Spirit while in his mother's womb and had the stain of original sin removed from him.

God bless,
Bro. Ignatius Mary