Sufficient iodine intake is extremely important in pregnancy as iodine is essential for brain development. Iodine requirements during pregnancy are increased by more than 50%.
Iodine deficiency can cause maternal and fetal hypothyroidism and impair neurological development of the fetus, depending on the timing and severity of hypothyroidism as to whether the most severe form of iodine deficiency manifests to cretinism (congenital abnormalities).
In moderate to severely iodine deficient populations, controlled studies have demonstrated that supplementing with iodine before or during early pregnancy can eliminate new cases of cretinism, increases birth weight, reduces rates of perinatal and infant mortality and generally increases development sources in young children by 10-20%.
Mild maternal iodine deficiency can cause thyroid dysfunction however the effects on the offspring’s cognitive and or neurologic function are uncertain.
Two meta analysis data found iodine deficient populations experienced an average reduction in IQ by 12-13.5 points.
A review paper of human studies re-evaluated the iodine requirements during pregnancy, lactation and the neonatal period. The review proposed that the iodine intake requirement during pregnancy is 250-300µg per day, during lactation is 225-350µg per day and during the neonatal period for the infant is 90µg per day.
The review discussed the range of urinary iodine measured (in a urinary iodine spot test) is to be between 150-230µg/L for optimal iodine nutrition during these three periods (pregnancy, lactation, neonatal period).
Interestingly in the Australian population mild to moderate iodine deficiency has been identified to be more common than once thought. A Melbourne study performed at Monash University in 2005 found that 48.4% of Caucasian pregnant women had urinary iodine excretion levels of below 50µg indicating an iodine deficiency. This emphasises the need for iodine supplementation in the preconception, pregnancy and lactation periods. Organising a urinary spot iodine excretion test is recommended to ensure you are covered here.
Delange F. 2007 “Iodine requirements during pregnancy, lactation and the neonatal period and indicators of optimal iodine nutrition” Public Health Nutrition / Volume 10 / Issue 12A / December 2007, pp 1571-1580
Hamrosi M A, Wallace E M, Riley MD. 2005 “Iodine status in pregnant women living in Melbourne differs by ethnic group” Asia Pac J Clin Nutr 14(1):27-31
Zimmermann M B. 2012 “The Effects of Iodine Deficiency in Pregnancy and Infancy” Paediatric and Perinatal Epidemiology Volume 26, Issue Supplement s1, pages 108–117, July 2012