Iodine status in pregnant women and their newborns: are our babies at risk of iodine deficiency?

OBJECTIVES

To determine whether pregnant women and their newborns show evidence of iodine deficiency, and to examine the correlation between maternal urine iodine concentration (UIC) and newborn thyroid-stimulating hormone (TSH) level.

DESIGN

A cross-sectional study.

SETTING

Hospital antenatal care services (March-May 2004) and private obstetrician clinics (June 2004) in the Central Coast area of New South Wales.

PARTICIPANTS

815 pregnant women (> or = 28 weeks' gestation) and 824 newborns.

MAIN OUTCOME MEASURES

World Health Organization/International Council for the Control of Iodine Deficiency Disorders criteria for assessing severity of iodine deficiency (recommended levels: < 20% of urine samples in a population with UIC < 50 microg/L; and < 3% of newborns with whole-blood TSH level > 5 mIU/L).

RESULTS

The median UIC for pregnant women was 85 microg/L, indicating mild iodine deficiency. Almost 17% of pregnant women had a UIC < 50 microg/L, and 18 newborns (2.2%) had TSH values > 5 mIU/L. There was no statistically significant linear correlation between neonatal whole-blood TSH level and maternal UIC (r = - 0.03; P = 0.4). Mothers with a UIC < 50 microg/L were 2.6 times (relative risk = 2.65; 95% CI, 1.49-4.73; P = 0.01) more likely to have a baby with a TSH level > 5 mIU/L.

CONCLUSION

The pregnant women surveyed were mildly iodine deficient. TSH values for their newborns were mostly within acceptable limits. Ongoing surveillance of the iodine status of NSW communities to establish trends over time is recommended.