[curryst]

You're right, just using the wrong terms. The baby's weight is fixed at mass * gravity, it doesn't change. What changes is the force required to accelerate the baby upwards, which is the delta between the force of gravity (the baby's weight) and any upward forces opposing that gravity. So if the baby pushes upward with it's feet to help you, you have to exert less force to lift the baby.

Scientifically speaking, the weight of an object cannot change unless gravity changes or it's mass changes. The forces required to accelerate that object in a particular direction vary wildly based on all kinds of things that exert a force on the object.

Off topic, but that does make me curious how "weight" works in an environment where you're exposed to more than one gravitational field. Like if you're close enough to two black holes to be affected by the gravity from both.