This page of the guide to Amnesia Rebirth contains a walkthrough of the chapter called The Mines. It covers e.g. what to do during delivery, how to get out of the mines, how to use the portal in the desert and how to finish chasing the doctor by reaching the Tower.
Chasing the doctor
This stage will start with... a childbirth scene. Your only task is to rotate the camera when Tasi starts looking sideways. You have to keep the camera back on the doctor who delivers the baby.
Once you regain full control of Tasi, you must chase the doctor through the mine. The chase is very linear and there are no obstacles along the way.
Upon reaching the surface you will experience a sandstorm - just keep going.
Ultimately, you should notice a portal in the desert in the distance, through which the doctor will pass. Go there and use the portal to move to an alternate dimension.
Reaching the Tower
In the final part of this short chapter you simply have to reach the gate at the base of the Tower. Opening it will load the last level of the game.