The relationship of maternal iodine status and neonatal thyrotropin concentration: a study in Southern Thailand.

Iodine deficiency disorder (IDD) is a global health problem. Previous studies in Southern Thailand have shown that the prevalence of goiter in schoolchildren is 3-5%, indicating that Southern Thailand is an iodine sufficient area. We conducted a study in pregnant women to determine their iodine status and whether there was an association between maternal urinary iodine excretion (UIE) and the neonatal thyrotropin (TSH) concentration. We recruited 244 pregnant women attending the antenatal clinic at Songklanagarind Hospital. Their mean age was 28.5 +/- 5.3 years (range 15-42) with a mean gestation age of 9.4 +/- 2.7 weeks (range 6-15). Ten ml urine was collected for UIE measurement. All women were delivered at Songklanagarind Hospital. The mean gestational age at delivery was 38.2 +/- 2.1 weeks (range 28-41). The median maternal UIE was 139.5 microg/l with 78 (32%) women having UIE below 100 microg/l. The median TSH of the infants was 4.14 mIU/l (range 0.30-17.89) with 88 (36.1%) of infants having TSH concentration above 5 mIU/l. Logistic regression analysis revealed that the odds ratio of pregnant women with UIE below 100 microg/l giving birth to infants with neonatal TSH above 5 mIU/l was 2.04 (95% confidence interval 1.17-3.66, p = 0.012). In conclusion, our findings demonstrate that 32% of pregnant women have UIE below 100 microg/l, and that UIE below 100 microg/l in pregnant women is associated with neonatal TSH concentration above 5 mIU/l. These findings suggest that iodine deficiency is prevalent in pregnant women in Southern Thailand.