title: Maternal urinary iodine concentration up to 1.0 mg/L is positively associated with birth weight, length, and head circumference of male offspring.
abstract: Adequate iodine status in early life is crucial for neurodevelopment. However, little is known about the effects of maternal iodine status during pregnancy on fetal growth. The present study investigated the potential impact of maternal iodine status during pregnancy on offspring birth size. This large prospective cohort study was nested in a Bangladeshi population-based randomized supplementation trial in pregnant women [MINIMat (Maternal and Infant Nutrition Interventions in Matlab)]. Urine samples obtained at 8 wk of gestation from 1617 women were analyzed for iodine and other elements, such as arsenic and cadmium, using inductively coupled plasma mass spectrometry. Anthropometric measurements at birth included weight, length, and head and chest circumference. Maternal urinary iodine concentrations (UICs) ranged from 0.020 to 10 mg/L, with a median of 0.30 mg/L. Below ∼1.0 mg/L, UIC was significantly positively associated with birth weight and length. Birth weight and length increased by 9.3 g (95% CI: 2.9, 16) and 0.042 cm (95% CI: 0.0066, 0.076), respectively, for each 0.1-mg/L increase in maternal UIC. No associations were observed between UIC and head or chest circumference. When we stratified the analyses by newborn sex, the positive associations between maternal UIC (<1 mg/L) and measurements of size at birth were restricted to boys, with no evidence in girls. Among boys, the mean weight, length, and head circumference increased by 70 g (P = 0.019), 0.41 cm (P = 0.013), and 0.28 cm (P = 0.031) for every 0.5-mg/L increase in maternal UIC. Maternal iodine status was positively associated with weight, length, and head circumference in boys up to ∼1 mg/L, which is well above the recommended maximum concentration of 0.5 mg/L. The associations leveled off at UIC ≥ 1 mg/L. Our findings support previous conclusions that the advantages of correcting potential iodine deficiency outweigh the risks of excess exposure.
authors.affiliation: Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden;
authors.forename: Filip
authors.initials: F
authors.lastname: Rydbeck
authors.affiliation: Centre for Reproductive Health, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh; and.
authors.forename: Anisur
authors.initials: A
authors.lastname: Rahman
authors.affiliation: Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden;
authors.forename: Margaretha
authors.initials: M
authors.lastname: Grandér
authors.affiliation: Department of Women's and Children's Health, International Maternal and Child Health, University Hospital, Uppsala, Sweden.
authors.forename: Eva-Charlotte
authors.initials: EC
authors.lastname: Ekström
authors.affiliation: Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden;
authors.forename: Marie
authors.initials: M
authors.lastname: Vahter
authors.affiliation: Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden; maria.kippler@ki.se.
authors.forename: Maria
authors.initials: M
authors.lastname: Kippler
mesh_terms: D000328:Adult; D001724:Birth Weight; D001827:Body Height; D019587:Dietary Supplements; D005260:Female; D047109:Fetal Development; D006257:Head / Q000254:growth & development*; D006801:Humans; D007455:Iodine / Q000172:deficiency / Q000652:urine*; D008297:Male; D009752:Nutritional Status; D011247:Pregnancy; D011248:Pregnancy Complications / Q000652:urine; D011446:Prospective Studies; D012737:Sex Factors; D055815:Young Adult
chemical_list: D007455:Iodine