A pregnant lady uses fluoridated drinking water. All of the following are true regarding exposure of the foetus to fluoride except:
There are different views regarding the passage of fluoride across the placenta.
Some authors have said that placenta acts as a complete barrier to fluoride, others have said that it is only partial. 
Some have said that the placenta only acts as a barrier when there is a sudden increase in the maternal plasma fluoride level.

Essentials of preventive and community dentistry 
Soben Peter 
5th edition
The placenta acts as a regulator and reduces the concentration of fluorides reaching the foetus
The placenta acts as a regulator and increases the concentration of fluorides reaching the foetus
Both
None