OBJECTIVETo study iodine nutrition of pregnant women in different occasions and thyroid function of their neonates.

METHODSUrinary iodine of pregnant women and their serum T(3), T(4), FT(3), FT(4) were determined by chloric acid-digestion thermostatic assay and RIA, TSH determination by IRMA; neonatal umbilical cord blood TSH was determined by ELISA.

RESULTSMedian urinary iodine of pregnant women were 206.3 microg/L, 161.4 microg/L, 203.3 microg/L at 10 - 14 (first occasion), 23 - 27 (second occasion) and 39 - 40 (third occasion) week but the percentage that lower than 100 microg/L were 14.6%, 17.1%, 11.1% respectively. Serum T(3), T(4) of pregnant women was significantly higher than those women of premarital health inspection (PHIW, P < 0.001). The difference of serum T(3), T(4) of pregnant women at 10 - 14 and 39 - 40 week was not significant. Serum FT(3), FT(4) of pregnant women at 39 - 40 week were 2.61 +/- 0.47 pmol/L and 5.50 +/- 1.57 pmol/L respectively. The difference of serum TSH concentration at third occasion and first occasion of pre-pregnancy was significant but the difference of TSH frequency distribution in three groups was not significant (chi(2) = 1.138, P > 0.5). Blood TSH median neonatal umbilical cord was 1.99 mU/L but the percentage that higher than 5 mU/L was 9.4%.

CONCLUSIONFor those areas with high iodized salt coverage, pregnant women had had sufficient iodine supplement and good thyroid function. The percentage of neonates from iodine sufficient pregnant women with TSH > 5 mU/L was lower than 10%. Using the normal range of nonpregnant FT(3) and FT(4) to estimate the thyroid function of pregnant women could cause mis diagnosis.