There may be situations in France were women do not have sufficient iodine intake during pregnancy. The nutritional needs for iodine are increased during pregnancy, mostly during the first trimester, for the use of the mother and the embryo and fetus. In France, a deficiency in available iodine has been demonstrated in the general population and in a population of pregnant women. Iodine deficiency may affect the mother (goiter, high TSH, low thyroxin levels) and new information points to a risk of retarded development in children born to women with low thyroxin levels during the first and second trimesters of pregnancy. Iodine deficiency can also induce transient high TSH levels in the newborn. The question raised by these new established facts is whether iodine supplementation should be proposed for all pregnant women, and this before the second trimester of pregnancy. Systematic screening for thyroid deficiency might also be useful at the end of the first trimester of pregnancy.