Hi,
A mum I know with 4 kids was talk to me about this the other day and she was saying that it's all about capacity. When you first have one baby it is hard but the older bubs get the easier it gets and you relax into it you learn and you develop the capacity to mostly be calm collected and find it easy to take care of one baby and she said the more kids you have you relax into the role and learn what works for you. She was saying if she has 4 kids given to her at one time she would have been hiding under a rock but as the years went on and the babies came her capacity grew!