Devaki's and Yasodha's story is that of the sacrifice of mother's for the good of humanity. In today's world many mother's tie their children to their apron strings. And every act of mother's are pardoned in the name of motherhood. She is a mother how can she allow kids to do something, she is a mother so she will defend her kid even if he is a criminal. She is a mother she knows what is best for the child.
Krishna's story is one that broke through all this myths. If Devaki suffered one of the worst traumas a woman can suffer by seeing six of her children murdered so that she can give birth to that one child who will save humanity. Then not only that for the welfare of the child she entrusted him with another woman and never saw him growing up.
Coming to Yasodha, this mother bought up the kid fed him, defended his naughtiness, punished him, still loved him and yet in the end parted with him so that he could go on to complete the mission for which he was born.
Both Devaki and Yasodha are treated at par as far as Krishna goes. Both their sacrifices are the reason because of which a great human being was given to world.
I have heard a saying which a mother tells " I was happy the day you were born, but I am happiest the day when the world looks at you and hails the mother who bought you on this earth"
History is replete with examples that if a mother wishes to hear the second line about her offspring then of course she has to let go of the ofspring. Sacrifice has to start from mother