Iodine use while Breastfeeding
Drugs containing Iodine: Iodine Tincture, Lugol's, Iodine Mild, Iodine Tincture Decolorized, Strong Iodine
Medically reviewed by Drugs.com. Last updated on Feb 19, 2019.
Iodine Levels and Effects while Breastfeeding
Summary of Use during Lactation
Iodine is an essential trace nutrient for all infants that a normal component of breastmilk. Infant requirements are estimated to be 15 mcg/kg daily in fullterm infants and 30 mcg/kg daily in premature infants. Systematic reviews and studies on iodine nutrition found that iodine in breastmilk is adequate in iodine-sufficient countries, but in countries with iodine fortification of foods, many mothers did not obtain adequate iodine and that additional supplementation was desirable. In iodine-deficient areas, supplementation of breastfeeding mothers with iodine appears to be more effective than direct supplementation of the infant in reducing infant iodine deficiency. The American Thyroid Association recommends that breastfeeding women should supplement their diet with a daily oral supplement that contains 150 mcg of iodine, but sustained iodine intake while breastfeeding that exceeds 500 to 1100 mcg daily should be avoided. A survey in the United States between 2011 and 2014 found that only 19% of lactating women used a dietary supplement that contained iodine.
The use of excessive amounts of iodine in the mother near term and during breastfeeding (e.g., seaweed soup) can increase breastmilk iodine levels and cause transient hypothyroidism in breastfed infants. The absorption of iodine can be marked after application to open wounds or mucous membranes. Exposure of mothers to unnecessary iodine who are or will be breastfeeding should be avoided or minimized to the extent possible by avoiding its use on maternal mucous membranes (e.g., vaginal use, wound therapy), avoiding prolonged contact time, avoiding repeated applications, and applying it to the smallest possible surface areas of the body. It is possible that maternal exposure to iodine near term could interfere with thyroid studies done as a part of newborn screening tests.
Maternal Levels. Iodine is a normal mineral in breastmilk that is essential for the infant's thyroid. Iodine concentrations are highest in colostrum, declining gradually as lactation progresses. Breastmilk iodine concentrations of 150 mcg/L during the first 6 months of lactation should be adequate to prevent infant iodine deficiency. The amounts of iodine in breastmilk vary with maternal iodine intake. A 1981-82 survey of 61 breastmilk samples from 37 women in North Carolina found a mean iodine concentration of 178 mcg/L (range 29 to 490 mcg/L). A 2002-06 survey of 57 women in the Boston area found a similar mean concentration of 205 mcg/L (range 2.7 to 1968 mcg/L) and a median iodine breastmilk concentration of 157 mcg/L. A study of 97 iodine-sufficient women in Switzerland compared two analytic methods. The ICP-MS standard curve method found a median iodine concentration of 245 mcg/kg in pooled milk samples from 25 women while the ICP-MS 129-I isotope ratio method found a median concentration of 183 mcg/kg in pooled milk samples of 66 women.
A study of 36 breastmilk samples from 18 different states in 2003-04 found a mean iodide breastmilk concentrations of 63.3 mcg/L (range 4.5 to 162 mcg/L). Another study of 108 breastmilk samples from 10 women by the same authors found a mean iodide concentration of 87.9 mcg/L (range 3.1-334 mcg/L), and a median concentration of 55.2 mcg/L. The reason for the differences in iodine values between these two studies and the above studies is not clear.
Two women were given potassium iodide orally. One was given 325 mg orally 3 times daily to a total of 3.6 grams and the other was given 650 mg orally 3 times daily to a total of 4.6 grams. Milk samples were obtained after the eighth and eleventh doses in the first woman and 2 hours after the last dose in the second woman. The first woman had milk iodide concentrations of about 33 and 29 mg/L and the second had a concentration of about 38 mg/L. The analytic method used in this old study was insensitive and imprecise by modern standards.
A woman developed an abdominal wall abscess 1 week after having a cesarean section. The abscess was treated with systemic antibiotics and the wound was packed with 60 sq. cm of iodine tampons, containing about 10.5 mg of iodine. On day 29 postpartum, her milk iodine was 4410 mcg/L (normal range 29 to 490 mcg/L). Her iodine therapy was stopped, and 2 days later milk iodine was about 1400 mcg/L; by day 40 postpartum, it was about 1000 mcg/L. By day 60 postpartum, the milk level was below 100 mcg/L.
The mother of a 31-week preterm infant packed her cesarean section wound with iodine-soaked gauze because of wound dehiscence and infection. Her breastmilk iodine concentration at 3 weeks postpartum was 1911 mcg/L (upper limit of normal 185 mcg/L).
The mothers of 31 preterm Korean infants was measured for iodine concentration on week 1, 3 and 6 postpartum. Korean mothers have elevated iodine levels from large amounts of dietary iodine in brown seaweed soup during the first month postpartum. Median breastmilk iodine levels were 2529, 1153 and 822 mcg/L at the 3 times, respectively.
A mother used an iodine antiseptic on her episiotomy wound for 10 to 12 days postpartum. At 15 days postpartum, her milk iodine level was 300 mcg/L (normal 100-200 mcg/L).
A mother ate large amounts of seaweed soup imported from China for the first 10 days postpartum to increase her breastmilk supply. Breastmilk iodine levels were much higher during the time of seaweed consumption at 878 mcg/L total iodine compared to 188 mcg/L 4 weeks later and 144 mcg/L 7 weeks later.
A study in northern Spain compared the milk iodide level of mothers taking a normal diet, including iodized salt and seafood (n = 14), with mothers on the same diet plus a supplement of 200 mg daily of potassium iodide (n = 46). The median breastmilk iodide levels from supplemented mothers of preterm infants was 0.172 mg/L in the supplemented mothers compared to 0.128 mg/L in the unsupplemented mothers. The median breastmilk iodide levels from supplemented mothers of fullterm infants was 0.178 mg/L in the supplemented mothers compared to 0.117 mg/L in the unsupplemented mothers. No statistical difference was found between preterm and fullterm milk iodide in either the supplemented or unsupplemented group. The authors conclude that in this iodine-sufficient area, unsupplemented mothers excrete sufficient amounts of iodide in breastmilk.
Sixteen lactating women were administered 752 mcg of potassium iodide (572 mcg iodine) in the morning afer an overnight fast. They also ingested an additional 36 to 685 mcg of dietary iodine during the study period. Breastmilk samples were obtained at baseline and every hour for 8 hours. Breastmilk iodide increased from an average of 46 mcg/L at baseline to a peak of 354 mcg/L. Peak iodine levels in milk occurred at an median of 6 hours (range 5 to 7 hours) after the dose of iodine.
A study in Thailand compared mothers supplemented with 200 mcg daily of iodine daily to unsupplemented mothers. Breast milk samples were collected from 57 lactating women, 33 of whom received iodine supplementation during pregnancy. The median breastmilk iodine concentration at 2 months postpartum was significantly higher in the supplemented mothers (109 mcg/L) than in nonsupplemented mothers 70 mcg/L).
A study in Iran, which is considered iodine deficient, compared iodine breastmilk content between control mothers and those supplemented with cow's milk fortified with 150 mcg of iodine per cup. Both groups used iodized salt. Iodine levels in breastmilk were greater in the supplemented group than in the control group at 10, 14 and 30 days, with the median levels ranging from 210 to 242 mcg/L compared to the control group which had median levels ranging from 142 to 162 mcg/L at the same times.
A study in Ethiopia compared administration of capsules containing 225 mcg of iodine given once daily to the provision of iodized salt containing 35 mcg/gram of iodine to mothers who were breastfeeding. At the end of 6 months no difference was found in median breastmilk iodine concentrations between the two groups. Forty-five percent of women had breastmilk iodine levels above 120 mcg/L, which is the level recommended for adequate infant iodine intake. The authors considered the two methods to be equivalent.
Twenty-three mothers in Japan were treated with potassium iodide for Graves disease. Doses were adjusted to maintain normal thyroid function; the median dose was 50 mg daily (range 10 to 100 mg/day). The median breastmilk iodine level was 15.05 mg/L (range 0.831 to 72 mg/L).
Thirty-six women in the Netherlands took a supplement containing 150 mcg of iodine daily during pregnancy and for 4 weeks postpartum. Milk samples from 33 of the women analyzed at 4 weeks postpartum contained 1.2 micromoles/L (304 mcg/L; range 0.05 to 3 micromoles/L).
A study in Iran randomized mothers to receive placebo (n = 51), 150 mcg (n = 50) or 300 mcg (n = 43) of iodine daily as potassium iodate for 12 months. Milk iodine levels were measured at 1, 2, 4, 6, and 12 months postpartum. In mothers who received iodine, median breastmilk iodine over the 12-month period was greater than in the placebo group. The iodine concentration was 1.39 times higher in the 300 mcg group than that in the 150 mcg group. Iodine milk levels slowly trended downward and at 12 months postpartum, levels in all groups was about 150 mcg/L.
Infant Levels. The preterm infants of Korean mothers with high levels of breastmilk iodine had relative high urinary iodine levels that were thought to be related to high maternal intake of iodine.
A woman developed an abdominal wall abscess 1 week after having a cesarean section. The abscess was treated with systemic antibiotics and the wound was packed with 60 sq. cm of iodine tampons, containing about 10.5 mg of iodine. On day 29 postpartum, her breastfed infant's urine contained 3932 mcg/L of iodine (normal range <185 mcg/L). By day 40 postpartum, the infant's urine iodine level was normal.
The mother of a 31-week preterm infant packed her cesarean section wound with iodine-soaked gauze because of wound dehiscence and infection. The urine iodine level of her 2-week-old breastfed neonate was 684 mcg/L (normal range 42 to 350 mcg/L).
A mother used an iodine antiseptic on her episiotomy wound for 10 to 12 days postpartum. At 15 days of age, her infant had a urinary iodine concentration of 410 mcg/L (normal 100 to 200 mcg/L).
Two mothers originally from Asia (Korea and China) reportedly ate large amounts of soup made from seaweed from their home countries in the postpartum period. The infants of both mothers had elevated urinary iodine levels. The Korean mother continued to eat the soup for several weeks postpartum. Her infant's urinary iodine levels were 391 mcg/L and 690 mcg/L (normal range 100 to 300 mcg/L) at 1 and 2 months postpartum. The Chinese mother ate large quantities of seaweed soup for the first 10 days postpartum to increase her breastmilk supply. Her infant's urinary iodine level at 4 weeks of age was 343 mcg/L or 5055 mcg/gram of creatinine (normal range 100 to 300 mcg/gram).
A study of 46 nursing mothers supplemented with 200 mg of potassium iodide daily measured the iodine content of their breastfed infants' urine. Urine iodide concentrations were 0.365 mg/L among preterm infants and 0.376 mg/L among fullterm infants.
A study in Thailand compared mothers supplemented with 200 mcg daily of iodine daily during pregnancy to unsupplemented mothers. At 2 months of age, exclusively breast-fed infants whose mothers received iodine supplementation (n = 11) had greater urinary iodine concentrations (381 mcg/L) than those whose mothers were not supplemented (n = 14; 216 mcg/L).
A study in Iran, which is considered iodine deficient, compared iodine breastmilk content between control mothers and those supplemented with cow's milk fortified with 150 mcg of iodine per cup. Both groups used iodized salt. Although iodine levels in infant urine were greater in the supplemented group than in the control group at 10, 14 and 30 days, these differences were not statistically significant and all infants were iodine sufficient.
A study in Ethiopia compared administration of capsules containing 225 mcg of iodine given once daily to the provision of iodized salt containing 35 mcg/gram of iodine to mothers who were breastfeeding. At the end of 6 months, no difference was found in the median urinary iodine concentrations between the two groups of breastfed infants. The authors considered the two methods to be equivalent.
Twenty-three mothers in Japan were treated with potassium iodide for Graves disease. Doses were adjusted to maintain normal thyroid function. Their 26 infants (1 pair each of twins and triplets) were breastfed, some exclusively and some partially. The median urinary iodine concentration in the infants' urine was 15.65 mg/L (range 0.157 to 250 mg/L). The infants' median free thyroxine level was 1.01 ng/dL (range 0.61 to 1.55 ng/dL) and median thyrotropin level was 2.1 microIU/mL (range 0.6 to 12.3 microIU/mL).
A study of infants between 4 and 6 months of age in Bangkok, Thailand measured urinary iodine levels in exclusively breastfed (n = 19), mixed breastmilk and formula (n = 17) and exclusively formula-fed (n = 35) infants. The median urinary iodine concentrations (UIC) of infants and lactating mothers was 282 and 149 mcg/L, respectively. Breastfed infants had a significantly higher median UIC than formula-fed infants. There was a positive correlation between infant and maternal UIC.
A study in Iran randomized mothers to receive placebo (n = 51), 150 mcg (n = 50) or 300 mcg (n = 43) of iodine daily as potassium iodate for 12 months. Among their breastfed infants, the urinary iodine concentration was >100 mcg/L in all groups at all times with no statistically significant differences between groups.
Effects in Breastfed Infants
In Switzerland, a girl born at 29 weeks of gestation with adequate size for gestational age showed negative TSH screening on day 5. Her mother developed an abscess of the abdominal wall 1 week after her cesarian section and the wound was packed with tampons containing about 10.5 mg of iodine. The baby's TSH was elevated to 23 milliunits/L on day 23, and 288 milliunits/L on day 29. Free thyroxine (T4) levels were decreased to 2.8 ng/L and free liothyronine (T3) with 1.52 ng/L, without signs or symptoms of hypothyroidism. Iodine contents of maternal milk and of infant urine were 4.4 mg/L and 3.9 mg/L, respectively. Treatment with levothyroxine was started, breastfeeding was discontinued and disinfection with iodine was stopped. The infant's thyroid function tests normalized after 6 days. The infant's abnormal thyroid function tests were probably caused by maternal iodine use.
The mother of a 31-week, 961 gram preterm infant packed her cesarean section wound with iodine-soaked gauze because of wound dehiscence and infection. She was expressing milk for her hospitalized infant. The infant's thyroid function tests were normal at birth, but at 2 weeks of age, the infant's serum thyroxine was borderline low and TSH levels were elevated. One week later, TSH had increased to 77 milliunits/L and both thyroxine and free thyroxine levels were low. Breastmilk was discontinued and levothyroxine was started. The mother discontinued the iodine packing and 1 week later breastmilk feeding was resumed. At 2 months of age, the infant's thyroid function test were normal while taking levothyroxine.
A study of 31 preterm infants born at 34 weeks gestational age or less was performed in Korea where mothers typically ingest large amounts of seaweed soup during the first month postpartum. Subclinical hypothyroidism was frequently found in the infants with high intake of iodine from breastmilk.
A mother used an iodine antiseptic on her episiotomy wound for 10 to 12 days postpartum. At 15 days of age, her infant had elevated TSH and low free T4 serum levels, an enlarged thyroid gland, and an elevated urinary iodine concentration. The infant's symptoms were probably related to maternal iodine application.
Two mothers originally from Asia (Korea and China) reportedly ate large amounts of soup made from seaweed from their home countries in the postpartum period. Their infants had elevated thyrotropin (TSH) levels when tested at 3 to 4 weeks of age and signs of hypothyroidism. Both were treated with thyroid hormones and regained normal thyroid function.
A 21-day-old breastfed (extent not stated) infant presented with unconjugated hyperbilirubinemia. Neonatal TSH screening was normal, but at 21 days it was 87.3 IU/L (normal 0.27 to 4.2 IU/L). Free T4 was 7.3 pmol/L (normal 12 to 22 pmol/L) and the thyroid was slightly enlarged. The infant's parents were of Korean origin and the mother had consumed 3 to 4 bowls of brown seaweed (Undaria pinnatifidia) soup daily from the time of birth. The infant's hypothyroidism was probably caused by the high iodine content of the seaweed soup.
Twenty-three mothers in Japan were treated with potassium iodide for Graves disease. Doses were adjusted to maintain normal thyroid function; the median dose was 50 mg daily (range 10 to 100 mg/day). Their 26 infants (1 pair each of twins and triplets) were breastfed, some exclusively and some partially. Twenty-five of the 26 infants had normal thyroid function. One 5-month-old infant presented with subclinical hypothyroidism, indicated by a blood thyrotropin level of 12.3 microIU/mL, after 1 month of maternal therapy. Two months after potassium iodide discontinuation, the blood thyrotropin level normalized to 2.3 microIU/mL. In other infants, thyrotropin levels deceased over time without discontinuing maternal iodine or breastfeeding.
A breastfed Korean infant was found to have an elevated TSH at 15 and 22 days of age and a low free T4 level at 22 days of age. The infant also had markedly elevated urine iodine levels. Her mother had been drinking seaweed soup almost daily during pregnancy and postpartum. The infant was started on levothyroxine and the mother told to feed the infant formula and stop breastfeeding temporarily. The mother resumed nursing at 1 month of age and levothyroxine was at a lower dose until 4 months of age. The infant's thyroid function remained normal up to 12 weeks off of levothyroxine. It is probable that the thyroid dysfunction was caused by excess iodine in breastmilk.
Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.
Alternate Drugs to Consider
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