Objective: To assess the iodine nutrition and thyroid function of pregnant women during different periods of pregnancy, to provide evidence for guiding iodine supplementation for them.
Methods: A cross-sectional survey was performed in 215 pregnant women in Yongjing couty from May to June 2013. Samples of blood and random urine were collected, and serum thyrotrophin (TSH), free triiodothyronine (FT3), free thyroxine (FT4), anti-thyroid peroxidase (anti-TPO), antithyroglobulin ( anti-TG)and urinary iodine were measured.
Results: The medians of urinary iodine from the three groups of pregnant women(first, second and third trimester) were 189.8 µg/L, 152.5 µg/L and 144.9 µg/L respectively. With the exception of pregnant women in the third trimester, the urinary iodine medians of pregnant women in the first and second trimesters were within the 150-249 µg/L range which was defined as optimal by WHO/UNICEF/ICCIDD. With the increase of gestational age, the level of FT3 decreased (P < 0.05), with the FT3 levels in the first trimester were higher than those in the second or third trimester (P < 0.05). The difference of TSH levels among the three groups of pregnant women was statistically significant (P < 0.01), with a U-shaped curve seen between the iodine TSH levels and the gestational age. The medians of anti-TG and anti-TPO appeared the lowest in the first trimester, and remained at a high level in women at second and third trimesters. Significant difference was seen in anti-TG, anti-TPO levels of the three groups of pregnant women (first, second and third trimester) (P < 0.01). The incidence of thyroid function disorder was 1.86%, including subclinical hypothyroidism accounted for 1.40%, and hypothyroidism accounted for 0.47%. The incidence of thyroid function disorder mainly appeared in the early pregnancy. Abnormal FT3, TSH, positive anti-TG and anti-TPO were mainly seen during early pregnancy. The changes of TSH, FT3, FT4, anti-TG and anti-TPO along with the changes of urine iodine levels were not obvious.
Conclusion: With the increase of gestational age, the incidence of iodine deficiency also increased among pregnant women. Abnormal thyroid hormones, TSH, positive anti-TG and anti-TPO were mainly existed in the early pregnancy. Programs as monitoring urinary iodine as well as thyroid function targeting all the pregnant women should be carried out.