Noncompliance to iodine supplementation recommendation is a risk factor for iodine insufficiency in Portuguese pregnant women: results from the IoMum cohort

Purpose After a recommendation for iodine supplementation in pregnancy has been issued in 2013 in Portugal, there were no studies covering iodine status in pregnancy in the country. The aim of this study was to assess iodine status in pregnant women in Porto region and its association with iodine supplementation. Methods A cross-sectional study was conducted at Centro Hospitalar Universitario Sao Joao, Porto, from April 2018 to April 2019. Pregnant women attending the 1st trimester ultrasound scan were invited to participate. Exclusion criteria were levothyroxine use, gestational age < 10 and >= 14 weeks, non-evolutive pregnancy at recruitment and non-signing of informed consent. Urinary iodine concentration (UIC) was measured in random spot urine by inductively coupled plasma-mass spectrometry. Results Median UIC was 104 mu g/L (IQR 62-189) in the overall population (n = 481) of which 19% had UIC < 50 mu g/L. Forty three percent (n = 206) were not taking an iodine-containing supplement (ICS) and median UIC values were 146 mu g/L (IQR 81-260) and 74 mu g/L (IQR 42-113) in ICS users and non-users, respectively (p < 0.001). Not using an ICS was an independent risk factor for iodine insufficiency [adjusted OR (95% CI) = 6.00 (2.74, 13.16); p < 0.001]. Iodised salt use was associated with increased median iodine-to-creatinine ratio (p < 0.014). Conclusions A low compliance to iodine supplementation recommendation in pregnancy accounted for a mild-to-moderately iodine deficiency. Our results evidence the need to support iodine supplementation among pregnant women in countries with low household coverage of iodised salt. Trial registration number NCT04010708, registered on the 8th July 2019.

Automated summary

This study aimed to assess iodine status in pregnant women in Porto region and its association with iodine supplementation. The findings revealed that pregnant women had poor but not severe iodine status, and most of them did not comply with iodine supplementation recommendations. The use of iodized salt and iodine-containing supplements were associated with improved iodine status.