Background: Maternal severe iodine deficiency has been associated with pregnancy and neonatal loss but the impact of mild-moderate iodine deficiency on pregnancy is not well-documented. Mild-moderate iodine deficiency during pregnancy is common even in iodine replete countries. In the UK women of reproductive age have been found to be mildly-to-moderately iodine deficient. UI/C is an optimal indicator for iodine status in pregnancy.
Aims: We investigated whether insufficient iodine status during pregnancy is associated with adverse obstetric outcomes defined as pregnancy or child loss by age 1 year or obstetric complications including pre-eclampsia, hypertensive disorders of pregnancy, glycosuria, anaemia, caesarean delivery, malpresentation, low/high birth weight percentiles, pre-term delivery, antepartum and post-partum haemorrhage.
Methods: We analysed outcomes of 3182 singleton pregnancies from the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. Mother-child pairs were selected based on availability of UI/C measurements. First, we compared UI/C in mothers with babies alive at 1 year to those with pregnancy/child loss (n=42). Next, we analysed the relationship between UI/C and pregnancy outcomes in 3140 pairs with live babies. We compared the incidence of outcomes in four UI/C categories: <50.0; 50149; 150250; 250+ μg/g. Additionally, we compared the UI/C as a continuous variable in those with and without a complication of interest.
Results: The median urinary iodine concentration in the entire cohort was 92.25 μg/L (classed as iodine insufficient) and the median UI/C 123.9 μg/L. There were no relevant demographic differences between the mothers with live babies and those who suffered loss. There were no statistically significant differences in median values of UI/C between the two groups. The incidence of studied outcomes did not differ among the four UI/C categories, nor were there any statistically significant differences in the median UI/C when stratified based on the studied outcomes.
Conclusion: Iodine-to-creatinine ratio was not associated with significantly different obstetric outcomes in an iodine-insufficient pregnant population.