Prevalence of post-partum thyroiditis in Liguria (Italy): an observational study.

BACKGROUND: Post-partum thyroiditis (PPT) is an autoimmune disorder occurring within the first year following delivery. A variable prevalence has been reported in different surveys. We prospectively evaluated PPT prevalence and outcome in a cohort of pregnant women living in a well-defined geographic area.

AIM: A subset from a group of healthy women consecutively evaluated for thyroid function and thyroid autoimmunity during pregnancy, referring to the same obstetric unit, were followed up at 4-6 months and 1 yr after delivery.

MATERIALS/SUBJECTS AND METHODS: Follow-up for PPT was performed in 258 pregnant women. Control data were obtained in a comparable group of healthy non-pregnant women. Free T3 (fT3), free T4 (fT4), TSH thyroglobulin/thyroid peroxidase autoantibodies (TgAb/TPOAb), and urinary iodine excretion were measured.

RESULTS: Autoantibody positivity was observed in 9.3% of pregnant, similar to control women. Forty-three out of 59 autoantibody-positive women were followed up; 23 showed PPT at the first control, 18 had hypothyroidism at 1 yr (5 had not shown PPT at the first control). Among 215 out of 584 autoantibody-negative women followed up, 27 developed PPT (15 of them without thyroid autoantibodies); 16 developed thyroid autoantibodies without PPT. After 1 yr, 9 women had hypothyroidism: only 1 of them was autoantibody-negative at the former control. Urinary iodine was increased in several pregnant women.

CONCLUSIONS: An overall PPT prevalence of about 18% may be estimated. PPT was also observed in autoantibody- negative women. Differences with other surveys may be related to both study protocol and characteristics of the population studied.