Iodine status of pregnant women residing in the urban Free State Province of South Africa is borderline adequate: The NuEMI study.

Adequate iodine nutrition during pregnancy is essential for optimal fetal development and neonatal outcomes. In South Africa, the iodine status of pregnant women, who have increased iodine requirements, is under-researched. We hypothesized that the iodine status of pregnant women in the Free State Province would be inadequate and may differ between urban and rural areas. This cross-sectional study included 430 urban and 187 rural pregnant women visiting antenatal clinics in the Free State. Urinary iodine concentration (UIC) was determined using the modified Sandell-Kolthoff reaction method, and serum thyroglobulin (Tg) was measured using the Q-Plex™ Human Micronutrient Array. Data on self-reported iodized salt use were collected using a questionnaire. Median (IQR) UIC was 155 (96-248) µg/L; 150 (94-235) µg/L in urban and 161 (106-256) µg/L in rural participants (P= 0.27), indicative of adequate iodine status. Median (IQR) Tg was 11.5 (7.1-20.4) µg/L, and was not significantly associated with UIC, even after controlling for maternal age and gestational age (urban P= 0.14; rural P= 0.48). The proportions of pregnant women who reported to use iodized household salt were 81% in urban and 70% in rural areas. Our results show that despite the widespread use of iodized salt, the median UIC of pregnant women residing in the urban Free State Province indicates only borderline adequate iodine status. A national iodine survey including pregnant women is recommended to determine the effectiveness of the South African salt iodization program in light of the current salt reduction policy.