Yes. From the very moment of his birth man has an angel guardian appointed to him, because those benefits which are conferred by God on man as a Christian, begin with his baptism (such as receiving the Eucharist, and the like), but those which are conferred by God on man as a rational being, are bestowed on him at his birth, for then it is that he receives that nature; among the latter benefits we must count the guardianship of angels.
Statim a nativitate habet homo Angelum ad sui custodiam deputatum quia beneficia quae dantur homini divinitus ex eo quod est Christianus, incipiunt a tempore Baptismi (sicut perceptio Eucharistiae, et alia huiusmodi), sed ea quae providentur homini a Deo, inquantum habet naturam rationalem, ex tunc ei exhibentur, ex quo nascendo talem naturam accipit; et tale beneficium est custodia Angelorum.
As long as the child is in the mother's womb it is not entirely separate, but by reason of a certain intimate tie, is still part of her: just as the fruit while hanging on the tree is part of the tree. And therefore it can be said with some degree of probability, that the angel who guards the mother guards the child while in the womb. But at its birth, when it becomes separate from the mother, an angel guardian is appointed to it.
Puer quandiu est in materno utero, non totaliter est a matre separatus, sed per quandam colligationem est quodammodo adhuc aliquid eius, sicut et fructus pendens in arbore, est aliquid arboris. Et ideo probabiliter dici potest quod Angelus qui est in custodia matris, custodiat prolem in matris utero existentem. Sed in nativitate, quando separatur a matre, Angelus ei ad custodiam deputatur, ut Hieronymus dicit.