What are the first indications doctors notice when realizing a patient has Munchausen's Syndrome?

I've run into a few over the years as a nurse & the first sign we (the nursing staff) noticed is that the child got sick during the day when mom was there but was fine during evenings & nights when the children were under our care. Moms also wanted to control the children's feedings & meals, often saying they brought in "special foods" that the kids preferred. The kids often started to vomit within an hour after these feedings. When we started to monitor the meals & refused to allow the mother to feed the kids, they got better. The doctors worked with us in telling the mother that the nurses had to do the feedings because we had to do "intake & output sheets" on how much was taken in (in cc' s which was very small measurements that the mother couldn't do). When you first met these mothers they appeared so concerned & doted over the children. We learned though that appearances can be very deceiving.