Evaluation of Iodine Supplementation in Women With Pregnancy Associated With Gestational Diabetes. IODIAB Study

Iodine supplementation is indicated by the French High Authority for Health (HAS) and by the World Health Organization (WHO) during pregnancy. We want to know if this supplementation is prescribed in a manner consistent with the HAS and WHO recommenations in women diagnosed with gestational diabetes mellitus. Results: Conclusion The objective of the Iododiab study is to assess whether practitioners caring for women with gestational diabetes mellitus prescribe iodine supplementation according to the recommendations of the French High Authority for Health and by the World Health Organization.


Introduction
In pregnancy we observe (i) increasing in serum thyroxine-binding globulin (TBG) concentrations, (ii) an elevation in renal blood ow and glomerular ltration which lead to an increased iodide clearance from plasma and, hence, to an obligatory loss of iodine. (iii) Increased activity of type 3 deiodinase in the placenta increases the degradation of thyroxine (T 4 ) to the inactive form reverse triodothyroinine (T 3 ) [1]. Thyroid hormone is essential for neurodevelopment both in utero and early in life [2], severe iodine de ciency causes a range of disorders which include hypothyroidism, goiter and profound impairment of growth and neurodevelopmental [3], it is well established that correcting severe iodine de ciency leads to better clinical outcomes, including reduced cretinism and infant mortality rates [4], of late there are concerns increasingly that even mild to moderate iodine de ciency leads to adverse clinical outcomes, including potentially reduced intelligence quotient (IQ) in offspring [5,6].
The physiological requirements for iodine are increased in pregnant women, going from 150 μg / day to 250 μg / day. The iodine intake is assessed by the iodine concentration in the urine, the target of which in pregnant women is ioduria between 150 and 250 μg / l [7]. In French the general population is not pregnant women is between 50 and 100 μg / l, which suggests a moderate iodine de ciency [10], [11], [12]. To maintain euthyroidism, the mother must increase its production of T4 by 40-50% (10-150%), which requires an additional iodine intake of 150-250 μg / d [13], [14], [15]. The thyroid contains a reserve of iodine, but this is depleted during pregnancy without supplementation. We wish to examine whether in women having a pregnancy bene ting from a personalized follow-up linked to a diagnosis of gestational diabetes, iodine supplementation is implemented according to WHO recommendations, ie 250 μg / day. Primary Evaluation Criterion: Iodic supplementation prescribed in μg / d Secondary objectives: evaluation of iodic supplementation according to prescriber (midwife versus general practician or gynecologist). Secondary evaluation criterion odic supplementation prescribed in μg / day by midwive, iodic supplementation prescribed in μg / prescribed by the general practitioner and iodic supplementation prescribed in μg / day by gynecologists.

Participants
Inclusion criteria: Pregnant woman with gestational diabetes con rmed by un abnormal fasting glucose or by oral hyperglycemia test, age ≥ 18 years, subject informed of the study and not having opposed it. Non-inclusion criteria: Already known thyroid pathology.
Key Data Collected and the outcome of the study Upon arrival at the reception consultation for the management of gestational diabetes, the information note will be given to the patient. During the consultation, the investigator will explain the study and obtain the patient's agreement to participate. The questionnaire will then be given to the patient.
There are no plans to follow up patients in this study. Participation consists of completing the questionnaire.
Data collected: The participants will answer to a questionary included the following questions: The term of pregnancy (in weeks), the parity (number of pregnancies), if the participants have a chronic pathology? If so, which one? which treatment? if the patient in known to have a pathology of the thyroid gland? If so, which therapy. Have the participant received a prescription for iodine supplementation since the start of pregnancy, If so, which one, for how long, at what dose. If there is iodic supplementation, who prescribed the prescription (midwife, attending physician, gynecologist. Are the lady receiving folic acid? During your previous pregnancies, did you receive vitamin supplementation? If yes which one?

Statistical justi cation for the sample size
We hypothesize that one in 2 patients receives iodine supplementation at 250μg / d. The number of patients is therefore 97 patients.

Description of statistical methods
The descriptive analysis will include for each quantitative parameter: mean, standard deviation, median, interquartiles, minimum, maximum. The qualitative parameters will be expressed by their number and corresponding percentage.
If p is the expected percentage, its con dence interval, considered at 20%, is: p + -1.96 * square root of ((p * (1-p) / n) If d is the distance between the estimate of the percentage and the bounds of its con dence interval, we must solve the equation: d = 1.96 * square root of ((p * (1-p) / n) => n = 1.96 ^ 2 * p * (1-p) /d^2.= 97 patients The analysis will be performed using R software (R version 3.5.0 (2018-04-23) © 2018 The R Foundation for Statistical Computing).

Discussion
Iodic supplementation during pregnancy is indicated according to the recommendations of the World Health Organization and by the high Health French authority , the main objective of the iodiab study is to assess whether the prescription of this supplement is respected by the wise. woman, the general