Really unusual for a Statutory Scottish birth cert to state how many children (or the order of births). The only exception was entries for 1855 and pre official reg. on the Old Parish Registers. Could there be any confusion with the writing on the statutory register entry you have? Is the writing clear or could it be something else?
We had possible entries for Mary Welsh in 1891 and 1901. No other children showed with her if we have the right entries for her. She may well have had more children but hard to think how you could begin searching for them except doing as you have done for Mary Ann's birth.
Monica
