Thyroid Function Throughout Pregnancy With and Without Iodine Supplementation

Overt maternal hypothyroidism and/or iodine deficiency during pregnancy are linked to mental retardation in their offspring. Iodine deficiency may lead to maternal hypothyroxinemia, and even mild hypothyroidism in predisposed women. Indeed, thyroid hormones are of paramount importance for fetal brain development. During the first trimester of pregnancy, the only thyroid hormones available to the fetus are from maternal origin. Later in pregnancy, fetal thyroid progressively starts producing thyroid hormone, providing that maternal iodine status is adequate (≥200-250 mcg/day). It has been shown recently that mild maternal hypothyroidism may be responsible for discrete neuropsychological impairment in her child, implying a potential benefit for early screening and care during pregnancy. Furthermore, iodine deficiency is extremely common in our area (Brucker-Davis et al 2004). However, there is no official recommendation for screening and prevention, as for gestational diabetes for example.

We propose to study healthy pregnant women, screened before 12 weeks of gestation and without thyroid disease. They will be randomized in 2 groups and will therefore take pregnancy tablets, iodine fortified or not (Oligobs Maxiode -150 mcg/j of iodine, vs Oligobs grossesse), in addition to appropriate nutritional advice. Their longitudinal study will involve:

• Evolution of thyroid function parameters in the 2 groups, with comparison of maternal thyroid volumes, maternal thyroid hormones levels and cord blood parameters, including thyroglobulin, during pregnancy and in postpartum.
• Establishment of reference ranges for thyroid parameters for each trimester of pregnancy.

This public health project rests on our expertise in the care of pregnancies with maternal endocrine and metabolic disease (Hieronimus et al 2003-2005) and on a close collaboration of our Departments within the Pole "Mother-Child", conveniently located at the same hospital. It will allow us to precise iodine deficiency screening and prevention in our population and to structure and optimize the care for women with thyroid disease screened early in pregnancy (opening of a specific clinic), in order to improve maternal and fetal prognosis

Inclusion criteria

• All women follow-up in the three months of the pregnancy in the CHU de Nice
• Maternal thyroid function is between and 0.1<TSH<2.5 mUI/l, 23>T4L>12 pmol/l
• Person over 18
• Signed lit Consent
• Give birth in the CHU of Nice

Exclusion criteria

• Allergy known in iodine
• Iodized surcharge defined by an iodurie> 400 mcg / l
• Catch of ongoing iodized vitamins of pregnancy
• Participation in another research protocol