[The passage of fluoride across the placenta. An intra-uterine study].

Until now, transplacental passage of fluoride could only be checked during delivery. Recent developments in fetal blood sampling techniques in utero have made it possible to study its passage in pregnancy. Two tablets of 2.212 mg of sodium fluoride (Zymafluor) were given to 11 women with an average age of 27 1/2 years whose pregnancies on an average had lasted 22 weeks. They were having prenatal diagnosis by ultrasound guided fetal blood sampling in any case. The levels of fluoride were measured by the use of a specific electrode before the mother took fluoride and 40 minutes after she had taken it in both maternal and fetal blood samples. The results were compared with a controlled group of 11 pregnant women with similar characteristics: maternal age, duration of pregnancy and basal maternal fluoride levels. Fetal blood levels of fluorides in mothers who had taken sodium fluoride was statistically higher than in the controlled group (2.6 mumol/l and less than 1 mumol/l); this demonstrates in a statistically significant way that fluoride passes across the placenta in the fifth and sixth months of pregnancy which is the time when the milk teeth start to develop in the uterus.