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Table 1 Maternal characteristics according to urinary iodine-to-creatinine ratio

From: Maternal iodine status, intrauterine growth, birth outcomes and congenital anomalies in a UK birth cohort

 All participants, n = 6637Iodine-to-creatinine ratio (sample split into thirds)
Lower third (< 67 μg/g), n = 2213Middle third (67 to 105 μg/g), n = 2212Higher third (> 105 μg/g), n = 2212
I:Cr (μg/g), geometric mean (99% CI)86.0 (84.5 to 87.5)48.5 (47.8 to 49.3)83.4 (82.8 to 84.0)157.2 (154.3 to 160.2)
I:Cr (μg/g), median (IQR)83.1 (59.4 to 121.2)51.4 (42.7 to 59.4)83.2 (74.4 to 93.3)146.1 (121.2 to 185.2)
UIC (μg/L), geometric mean (99% CI)70.8 (69.1 to 72.5)45.9 (44.2 to 47.8)70.0 (67.6 to 72.6)110.4 (106.4 to 114.5)
UIC (μg/L), median (IQR)76.2 (44.6 to 120.2)52.2 (29.1 to 78.0)77.4 (47.3 to 112.5)117.6 (71.8 to 178.8)
Age (years), mean (SD)27.2 (5.6)26.5 (5.5)27.3 (5.6)27.8 (5.6)
BMI (kg/m2), mean (SD)25.8 (5.5)26.5 (5.8)25.9 (5.4)25.1 (5.1)
Socioeconomic status
 Least deprived and most educated1241 (21)307 (16)429 (22)505 (25)
 Employed, not materially deprived1231 (21)335 (17)440 (22)456 (23)
 Employed, no access to money917 (16)320 (16)295 (15)302 (15)
 Receives benefits, not materially deprived1594 (27)633 (32)505 (26)456 (23)
 Most economically deprived920 (16)360 (18)293 (15)267 (13)
Ethnic background, n (%)
 White British and European2877 (44)800 (36)1016 (46)1061 (48)
 Pakistani2827 (43)1064 (48)914 (42)849 (39)
 Others (Black, Indian, mixed, others)901 (14)337 (15)271 (12)293 (13)
Parity
 02931 (44)933 (42)966 (44)1032 (47)
 11859 (28)600 (27)623 (28)636 (29)
 21059 (16)371 (17)361 (16)327 (15)
 3+788 (12)309 (14)262 (12)217 (10)
Health and lifestyle in pregnancy
 Gestational diabetes, n (%)499 (8)152 (7)167 (8)180 (8)
 Pre-pregnancy hypertension, n (%)50 (0.8)21 (1.0)17 (0.8)12 (0.5)
 Pregnancy-induced hypertension, n (%)375 (6)125 (6)126 (6)124 (6)
 Preeclampsia, n (%)173 (3)61 (3)55 (2)57 (3)
 Drank any alcohol, n (%)958 (14)299 (14)335 (15)324 (15)
 Smoked, n (%)969 (15)302 (14)352 (16)315 (14)
 Used any supplements, n (%)1334 (20)213 (10)382 (17)739 (33)
 Iodine-containing supplements, n (%)988 (15)123 (6)264 (12)601 (27)
 White fish intake* (g/day), mean (SD)21.0 (27.0)18.7 (26.3)22.1 (28.2)22.1 (26.1)
 Oily fish intake* (g/day), mean (SD)1.4 (3.8)1.0 (3.2)1.5 (4.2)1.7 (4.0)
 Total fish intake* (g/day), mean (SD)23.8 (29.3)20.8 (28.3)25.1 (30.7)25.4 (28.8)
Eat 5 fruits/vegetables per day*, n (%)
 Always422 (19)122 (16)160 (21)140 (19)
 Sometimes1700 (75)601 (77)558 (72)541 (75)
 Never151 (7)57 (7)52 (7)42 (6)
  1. BMI body mass index, CI confidence intervals, I:Cr urinary iodine-to-creatinine ratio, IQR interquartile range, SD standard deviation, UIC urinary iodine concentration
  2. *Data from women who were asked about diet in pregnancy (n = 2776)
  3. Refer to supplement table S1 for details