Thyroid disorders and iodine nutritional status in the first trimester of pregnancy

Thyroid alterations are frequent during pregnancy and can be harmful to the development of the newborn. The objective of this study was to assess the prevalence of thyroid disorders as well as iodine nutritional status in pregnant women in the first trimester of pregnancy.

We performed a descriptive observational survey in a health area of Toledo (Spain). Participants consisted of pregnant women in this area and a control group of non-pregnant women of similar age. Both groups underwent thyroid ultrasonography and urinary iodine concentration test. Thyrotropin, free T4 and anti-thyroid peroxidase antibodies (anti-TPO Ab) levels were also measured in pregnant women.

A total of 199 expectant women and a control group of 169 non-pregnant women participated. The median urinary iodine concentration was 135 μg/l (IR, 240-65) in pregnant women and 150μg/l (IR, 200-90) in the control group. The mean values for TSH and free T4 in pregnant women were 1.95±1.62 and 1.03±0.15μU/ml, respectively. The prevalence of hypothyroidism in expectant women was 9.5% (95% CI, 6.0-14.7). Thyroid volume was larger in pregnant women (12.2±5.6mL) than in controls (10.7±4.0mL) (p=0.005). Thyroid nodules were found in 38.5% of the women in the control group and in 33.2% of pregnant women (p = 0.290).

Iodine status was deficient in our group of pregnant women. In agreement with the results of other studies performed in Spain, the prevalence of hypothyroidism was high. Thyroid hormones and anti-TPO Ab tests should be evaluated in the first prenatal visit. The prevalence of nodules was similar in pregnant women in the first trimester of pregnancy and in controls. Thyroid ultrasonography should be performed in pregnant women whenever a goiter and/or thyroid nodules are detected during clinical examination.