Time lines seem to be about 6 weeks of little to no intense activity. Walking is great. The body and organs are returning to it's original state after having the Uterus pushed to extremes.
After that mark, it's really becomes very individual to how well people handle different stresses. It's recommended that you can start strength training again, but very bouncy activities may be to much at this point.
Remember that the hormones that are in pregnancy will last up to 4 months after you stop breastfeeding. So Relaxin is still being in the system after birth. This is the hormone that allows ligaments to get loose so that a birth can take place.
You are more unstable.
It may take up to 2 years for your abdominal muscles to return to the strength and length you possessed pre birth.
One of the key points I've noticed is the lack of synergy between the hip muscles and your core muscles (ab muscles). Things like the obliques and hip abductors seem to be not "working" together as well as they could be.
Things like side planks off your knees and diagonal sits exercises are great primers to begin getting these guys working well together.
Exercises that make the lat and Glute work together are also highly recommended to get the bodies cross X pattern stronger.
In the end it is very individualist after about 8 weeks. But, doing certain exercises that help to increase stability will give you a jump start on getting back to being the active, dynamic athlete you were.