Is it ok to eat LCHF (low carb high fat) if you are pregnant or breastfeeding?

Yes it is!

LCHF is natural healthy food.  As simple as that...
 

The new mommy:

• stays healthy,
• gets less swollen (she won't carry as much water retention)
• gains normal amount of weight during pregnancy
• provides the unborn baby with all the nourishment it needs

If you are swollen for eg around ancles, feet and calves then you can also try to cut out or at least cut down on fruit.  Eat berries instead, but in moderation.  Fructose is not good for anyone.  The nourishment you will still get from veg and good protein products of high quality!
 
I don't have any proof of this, it's what I have learned through tallking to those that are in the same situation, by reading on the subject and through own experiences, experiences of others and encounters with specialists that work with pregnancy and babies.

LCHF is perfect for the pregnant mommy-to-be and for those new moms that are breastfeeding.  I am without doubt! 

Natural food is the best for any body, for all, always.