Prior research suggests that severe
iodine deficiency in pregnancy may be associated with
stillbirth. However, the relationship between mild to moderate
iodine insufficiency, which is prevalent even in developed countries, and risk of
stillbirth is unclear. We thus examined associations of
iodine status and risk of
stillbirth in a prospective population-based nested case-control study in Finland, a mild to moderately
iodine insufficient population.
Stillbirth cases (n = 199) and unaffected controls (n = 249) were randomly selected from among all singleton births in Finland from 2012 to 2013. Serum samples were collected between 10 and 14 weeks gestation and analysed for
iodide,
thyroglobulin (Tg) and
thyroid-stimulating hormone (TSH). Odds ratios (
ORs) and 95% confidence intervals (CIs) for
stillbirth were estimated using logistic regression. After adjusting for maternal age, prepregnancy body mass index, socio-economic status and other factors, neither high nor low serum
iodide was associated with risk of
stillbirth (Q1 vs. Q2-Q3 OR = 0.92, 95% CI = 0.78-1.09; Q4 vs. Q2-Q3 OR = 0.78; 95% CI = 0.45-1.33). Tg and TSH were also not associated with risk of
stillbirth in adjusted models. Maternal
iodine status was not associated with
stillbirth risk in this mildly to moderately
iodine-deficient population. Tg and TSH, which reflect functional
iodine status, were also not associated with
stillbirth risk. The lack of associations observed between serum
iodide, TSH and Tg and risk of
stillbirth is reassuring, given that
iodine deficiency in pregnancy is prevalent in developed countries.