WASHINGTON — More than 70% of women with access to dietary iodine may remain at risk for unrecognized iodine deficiency during pregnancy, based on results from an observational study conducted in 53 pregnant women in Canada.
The average urinary iodine concentration (UIC) was 111.3 mcg/L (range, 21.2–373.0 mcg/L) in this group of women. This average was below the range of 150–249 mcg/L that the World Health Organization recommends for pregnant women, said Dr. Pamela Katz, who presented the findings at the annual meeting of the International Society of Obstetric Medicine.
“Iodine receives little attention in North America,” said Dr. Katz. Adequate iodine intake is not considered a problem in North America, but this assumption may be inaccurate, she said.
It is recommended that pregnant women consume 200–300 mcg of dietary iodine daily. Dietary intake of iodized salt is the most common source of iodine for pregnant women in North America, although many prenatal vitamins contain iodine.
To determine whether women living in areas considered iodine sufficient were consuming adequate iodine, Dr. Katz and her colleagues at the University of Toronto and Mount Sinai Hospital, also in Toronto, measured the UIC of 53 women with an average age of 33 years during standard prenatal visits to the hospital. The average gestational age was 26 weeks.
With a UIC range of 21.2–373.0 mcg/L, only 21% of the women had a UIC within the recommended range of 150–249 mcg/L, while 71% were below the range and 8% were above it.
The study was limited by its lack of information on maternal diet and fetal outcomes, and the results may not be generalizable to other regions.
The reason for the reduced UIC remains unclear, but the results are consistent with data from larger studies, and it may be that women in some iodine-sufficient areas are consuming less salt as part of their diets, Dr. Katz said.
The findings suggest a greater need for increased awareness of the importance of iodine for a healthy pregnancy, and the iodine content of prenatal supplements should be standardized to meet the increased requirements of pregnancy, she emphasized.
Physiological changes associated with pregnancy, including increased renal clearance of iodine and the iodine requirements of the fetus, require additional iodine intake. Maternal iodine deficiency has been associated with an increased risk of complications including stillbirth and spontaneous abortion, as well as developmental problems in children, including developmental delay and mental retardation, Dr. Katz noted.