Amniotic fluid iodine concentrations do not vary in pregnant women with varying iodine intake

Abstract

Iodine deficiency is an important clinical and public health problem. Its prevention begins with an adequate intake of iodine during pregnancy. International agencies recommend at least 200 mg iodine per d for pregnant women. We assessed whether iodine concentrations in the amniotic fluid of healthy pregnant women are independent of iodine intake. This cross-sectional, non-interventional study included 365 consecutive women who underwent amniocentesis to determine the fetal karyotype. The amniocentesis was performed with abdominal antisepsis using chlorhexidine. The iodine concentration was measured in urine and amniotic fluid. The study variables were the intake of iodized salt and multivitamin supplements or the prescription of a KI supplement. The mean level of urinary iodine was 139·0 (SD 94·5) mg/l and of amniotic fluid 15·81 (SD 7·09) mg/l. The women who consumed iodized salt and those who took a KI supplement had significantly higher levels of urinary iodine than those who did not (P¼ 0·01 and P¼0·004, respectively). The urinary iodine levels were not significantly different in the women who took a multivitamin supplement compared with those who did not take this supplement, independently of iodine concentration or multivitamin supplement. The concentrations of iodine in the amniotic fluid were similar, independent of the dietary iodine intake. Urine and amniotic fluid iodine concentrations were weakly correlated, although the amniotic fluid values were no higher in those women taking a KI supplement. KI prescription at recommended doses increases the iodine levels in the mother without influencing the iodine levels in the amniotic fluid. Iodine: Amniotic fluid: PregnancyAlthough marked physiological differences exist between the maternal and fetal thyroids, both systems interact through the placenta and the amniotic fluid, modulating the transfer of iodine and small but biologically important amounts of thyroid hormones from the mother to the fetus (1) . Prior to the end of the first trimester, when the fetal thyroid gland and the pituitary-thyroid axis become functional, the thyroid hormones required by the fetus are all obtained from the maternal circulation (2) .The volume and content of amniotic fluid is the result of a balance between the urine and the fetal pulmonary fluids, the amount of fluid that is reabsorbed or swallowed by the fetus (3) and transfer of water and solutes across the fetal membranes.Animal studies have demonstrated a rapid exchange between the mother and fetus and between the fetus and the amniotic fluid, suggesting that the amniotic fluid could act as an iodine reservoir for the fetus (4) . Etling et al. (5) found high levels of iodine in the amniotic fluid of women who had undergone urographic examinations with iodized contrast materials or who had been exposed to iodized agents vaginally. However, few studies have investigated the iodine concentration in the amniotic fluid of human subjects and these only examined the influence of the overload of high iodine concentrations. ...

Bioactive Components in Human Milk Along the First Month of Life: Effects of Iodine Supplementation during Pregnancy

“…In this regard, we have found that KI supplements are as effective as multivitamins to reach adequate UIC. However, for BMIC, the differences among the 3 groups are not significant, probably due to 2 different facts: (a) the transport of iodine against a high-concentration gradient performed by the Na(+)/I(-) symporter tends to achieve higher BMIC even in women who had very low UIC, and (b) the effectiveness of multivitamins to increase BMIC might not be as effective as KI supplements, similar to what happens in amniotic fluid [15] . In our previous study in lactating women [11] , iodine in breast milk was negatively associated with different oxidative stress markers and with adiponectin levels.…”

Iodine Status of the U.S. Population, National Health and Nutrition Examination Survey 2003–2004

“…Pregnant women had higher median levels and lower prevalence of low levels than nonpregnant women. These findings can reflect a difference in renal clearance or dietary intake of iodine among these women (21,22). Further work is necessary to better define the causes of these differences and to achieve prevalence data that are representative of pregnant women in the United States.…”

Urine Iodine Levels in Preeclamptic and Normal Pregnant Women

“…Those women who had taken multivitamin supplements, however, showed no change in their UICs, even though many of these preparations contain variable amounts of iodine. Garcia-Fuentes et al [43] claims that, in order to achieve the objective of an adequate iodine intake during pregnancy, an active prescription of an iodine preparation that can be administered independently is preferable [43]. Magnesium plays an important role in numerous biochemical processes, which could have a protective effect on the developing fetus' brain [13].…”