Hello Sue
I too am glad you have asked this question as I would like to know the answer to your question too. My father-in-law was also born at Sandygate House, Wath Upon Dearne in 1941 but his parents lived on Alma Road, Rotherham.
I am presuming it had something to do with the war or may be a lack of midwifes but could be wrong, or may be the mothers were in a poor state of health and needed specialist attention. It is an interesting question to get an answer too, may be we can solve the mystery between us both, unless some one can help us out and point us in the general direction. If I find out before hand I will let you know.
Until then happy hunting.
Joy