Vaginal douching with polyvinylpyrrolidone iodine (PVP-I) during pregnancy results in maternal iodine overload and increases the iodine content of amniotic fluid. We evaluated the possible effects of this therapy on the thyroid of the fetus by investigating 62 women with a mean duration of amenorrhea of 20 weeks who solicited controlled abortion. Nineteen of them douched daily with PVP-I for 7 consecutive days before abortion (treated group). The other 43 women were not treated (control group). In both groups the iodine content was determined in the fetal thyroid and in amniotic fluid and maternal urine at the time of abortion. In addition, in the treated group the concentrations of iodine were also determined in amniotic fluid and urine before therapy and in urine after 4 days of therapy. There were no differences in the concentrations of iodine in urine and amniotic fluid in the control group and in the treated group before therapy. In the treated group urinary iodine increased from 6.1 ± (SEM) 0.8 µg/dl before therapy to 91 ± 20 µg/dl after 4 days and to 153 ± 60 µg/dl after 7 days of therapy (p < 0.001). In parallel, iodine in amniotic fluid increased from 1.2 ± 0.2 µg/dl before therapy to 3.7 ± 1.3 µg/dl after 7 days (p < 0.05). In both groups the iodine content of the fetal thyroid increased with gestational age. However, it increased more rapidly in the treated group (from 1 to 7.7 µg) than in the control group (from 1 to 2.5 µg), p < 0.05. In conclusion, routine vaginal douching with PVP-I during early pregnancy induces maternal iodine overload and markedly increases the iodine content not only of the amniotic fluid but also of the fetal thyroid, as soon as the trapping mechanism of iodide by the thyroid has started to develop. In view of the well-documented hypersensitivity of the fetal and neonatal thyroid to the blocking effect of excess iodide, the vaginal application of PVP-I is not recommended during pregnancy.

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