If you can identify and differentiate peaks in the 1H NMR corresponding to the sialyllactose and lactose protons, you could use the peak integrals to get an approximate ratio of your products.
I don't know how easy this is going to be, since we are talking about a complex spectrum you may have some issues with overlapping peaks etc.
Maybe try looking at the ratio of the protons at the anomeric positions, as these should be fairly well outside the most crowded region. You may have issues with the water peak overlapping with these though (I´m guessing you're in D2O). Without seeing the spectrum, I can't be sure this is a feasable method. In any case, it is not very accurate.
Could the components be separated on reverse phase silica perhaps?