A team of researchers at the Neurotoxicology Division of the EPA have determined that fluoride is a "developmental neurotoxicant" one of about 100 chemicals with "substantial evidence" (highest category) for toxicity to the developing mammalian nervous system.
On the list are substances pregnant women should minimize or strictly avoid:
Amphetamine, Arsenic, Bisphenol A, Cocaine, Methylmercury
Caffeine, Ethanol (Alcohol), Fluoride, Nicotine, and Lead*
Mundy WR, Padilla SJ, Shafer TJ, et al.
Building a database of developmental neurotoxicants:
Evidence from human and animal studies