I assume that you mean the Canon SD870IS camera flash.
I don't find any way to manually adjust the flash intensity.
If the room is well lit, the flash intensity will be less.
If it is daytime, in a room with a window near the child, the camera will use much less flash.
I don't recommend that you use flash with a new born, if the baby has it's eyes open.
I have used the flash if the baby's eyes are closed.
And newborn babies have their eyes closed most of the time anyway.
You can try a light deflector.
Tape some card stock over the flash so that you can bend the card stock enough that it deflects the flash upward at about a 45 degree angle. This also gives a softer light.
The other option is to turn the flash off.
But if you are indoors, you will need to put the camera on a tripod to prevent camera movement, as the exposure time will be close to a second (maybe more).
is there option in canon 870 to reduce or increase the flash intensity? it is too bright while taking pictures of my newborn.