Low or even no carb is always safe, is my understanding. Carbs is the one macronutrient which is not essential, this statement being an irrefutable fact. Even the hardest nosed nutritionist of the modern high-carb school must admit this. If our bodies need glucose, we make our own glucose from protein and fat.
And, here is the clincher, carbs is the one macronutrient which has a toxic effect on those with diabetic bodies, whether from an autoimmune disease (type 1), or the various kinds of type 2.
Now, if you said 'has anyone got any experience of maintaining a low protein/fats/water diet during pregnancy? Is it safe during pregnancy?' The answer would be a resounding 'No!'