That's one of my favourite Marian hymns. (My other two happen to be 'Sing we of the Blessed Mother' and 'Hail, all hail great Queen of Heaven', all of which happen to have great tunes.) But that's aside. My parish's hymnal contains that hymn, but in a horrible bastardised version that isn't the version I know. In the version I know, the first verse went "The God whom earth and sea and sky adore and laud and magnify,whose might they own,whose praise they swell,in Mary's womb vouchsafed to dwell." Whereas the one in the hymnal goes "The God whom earth and sea and sky adore and praise and magnify, whose might they claim whose love they tell, In Mary's body comes to dwell."
That's not only it. The last verse too gets re-written. I know it as "O Lord, the Virgin-born, to thee, eternal laud and glory be, whom with the Father we adore and Holy Ghost forevermore." Whereas the hymnal puts it as "O Lord, the Virgin-born to you Eternal praise and thanks are due, Whom with the Father we adore And Spirit blest forevermore."
It gets worse though. While the hymnal puts it to the tune Eisenach, which is good, they put "Sing we of the Blessed mother" to Omne Die. Which is a nice tune, But I always knew it 'Rustington'.
That's the problem with Roman Catholic hymnals: Even when they do pick good hymns (Like my parish's hymnal does: The: majority of the hymns are also in the U.S. Hymnal 1982 and some (five or six) are from the New English Hymnal) They have to justify themselves by messing around with the words and putting it to a different tune.
Same thing they did with "By all your Saints still striving".