Table 3 Use of iodine-containing supplements and pregnancy and birth outcomes

Odds ratio (95% CI)

p value

Odds ratio (95% CI)

p value

Odds ratio (95% CI)

Intrauterine death

270/78,318 (0.34%)

 Any iodine supplement use GW 0–20

29,131

0.80 (0.62, 1.03)

0.089

0.78 (0.61, 1.02)

0.071

0.96 (0.64, 1.45)

  Never (non-supplement user)

49,187 (13,451^b)

1 (ref.)

1 (ref.)

1 (ref.)

  Before pregnancy^c

7477

0.79 (0.51, 1.23)

0.30

0.76 (0.48 1.19)

0.23

0.92 (0.53, 1.62)

  GW 0–12

7149

0.94 (0.62, 1.42)

0.77

0.92 (0.60, 1.40)

0.70

1.11 (0.63, 1.94)

  GW > 12

5253

0.77 (0.45, 1.30)

0.32

0.76 (0.45, 1.29)

0.31

0.78 (0.38, 1.60)

Preeclampsia

2936/78,318 (3.8%)

 Any iodine supplement use GW 0–20

29,131

0.98 (0.91, 1.06)

0.64

0.93 (0.86, 1.01)

0.098

0.94 (0.84, 1.06)

  Never (non-supplement user)

49,187 (13,451^b)

1 (ref.)

1 (ref.)

1 (ref.)

  Before pregnancy^c

7477

0.88 (0.77, 1.01)

0.067

0.85 (0.74, 0.98)

0.022

0.84 (0.71, 1.00)

  GW 0–12

7149

1.05 (0.92, 1.19)

0.48

0.96 (0.84, 1.10)

0.58

0.97 (0.82, 1.14)

  GW > 12

5253

0.99 (0.86, 1.15)

0.93

0.93 (0.80, 1.08)

0.35

0.91 (0.76, 1.11)

Preterm delivery (< GW 37)

3889/77,995 (5.0%)

 Any iodine supplement use GW 0–20

29,014

1.00 (0.93, 1.07)

0.98

0.97 (0.91, 1.04)

0.42

1.07 (0.96, 1.18)

 First report of iodine supplement

  Never (non-supplement user)

48,981 (13,405^b)

1 (ref.)

1 (ref.)

1 (ref.)

  Before pregnancy^c

7445

1.07 (0.96, 1.20)

0.21

1.05 (0.94, 1.18)

0.35

1.18 (1.03, 1.36)

  GW 0–12

7126

1.02 (0.91, 1.14)

0.70

0.99 (0.88, 1.11)

0.82

1.08 (0.94, 1.25)

  GW > 12

5230

1.02 (0.90, 1.17)

0.71

0.99 (0.87, 1.13)

0.86

1.04 (0.89, 1.23)

Early preterm delivery (< GW 32)

612/77,995 (0.78%)

 Any iodine supplement use GW 0–20

29,014

0.82 (0.69, 0.97)

0.020

0.80 (0.67, 0.95)

0.010

0.82 (0.64, 1.05)

  Never (non-supplement user)

48,981 (13,405^b)

1 (ref.)

1 (ref.)

1 (ref.)

  Before pregnancy^c

7445

0.94 (0.72,1.24)

0.67

0.94 (0.71, 1.24)

0.66

0.98 (0.71, 1.38)

  GW 0–12

7126

0.83 (0.62,1.12)

0.22

0.80 (0.60, 1.08)

0.14

0.73 (0.51, 1.08)

  GW > 12

5230

0.61 (0.41, 0.90)

0.014

0.59 (0.40, 0.87)

0.008

0.62 (0.39, 0.98)

Spontaneous preterm delivery (< GW 37)

2211/76,313 (2.8%)

 Any iodine supplement use GW 0–20

28,406

1.03 (0.95, 1.13)

0.45

1.00 (0.91, 1.09)

0.93

1.09 (0.95, 1.25)

  Never (non-supplement user)

47,907 (13,196^b)

1 (ref.)

1 (ref.)

1 (ref.)

  Before pregnancy^c

7273

1.08 (0.94, 1.25)

0.28

1.07 (0.92, 1.24)

0.39

1.20 (1.00, 1.44)

  GW 0–12

6977

1.08 (0.93, 1.25)

0.31

1.02 (0.88, 1.19)

0.75

1.12 (0.93, 1.35)

  GW > 12

5123

1.09 (0.93, 1.29)

0.29

1.04 (0.88, 1.23)

0.65

1.12 (0.91, 1.38)

Beta (95% CI)

Beta (95% CI)

Beta (95% CI)

Birth weight

78,210

 Any iodine supplement use GW 0–20

29,091

− 11.0 (− 19.4, − 2.7)

0.009

13.6 (5.6, 21.7)

0.001

3.3 (−8.3, 14.8)

  Never (non-supplement user)

49,119 (13,435^b)

0 (ref.)

0 (ref.)

0 (ref.)

  Before pregnancy^c

7462

− 5.1 (− 19.1, 8.9)

0.48

16.3 (2.7, 29.9)

0.019

7.5 (− 9.0, 23.9)

  GW 0–12

7139

− 12.4 (− 26.4, 1.6)

0.084

19.6 (6.0, 33.1)

0.005

9.7 (− 6.8, 26.2)

  GW > 12

5248

− 11.7 (− 27.7, 4.3)

0.15

16.8 (1.4, 32.2)

0.033

12.0 (− 6.5, 30.4)

Birth weightz-score

77,949

 Any iodine supplement use GW 0–20

28,998

− 0.03 (− 0.04, −  0.01)

0.001

0.03 (0.01, 0.04)

< 0.001

0.01 (− 0.01, 0.03)

  Never (non-supplement user)

48,951 (13,393^b)

0 (ref.)

0 (ref.)

0 (ref.)

  Before pregnancy^c

7439

0.00 (−0.02, 0.03)

0.88

0.05 (0.03, 0.07)

< 0.001

0.04 (0.01, 0.07)

  GW 0–12

7121

− 0.03 (− 0.05, − 0.00)

0.043

0.04 (0.02, 0.07)

< 0.001

0.03 (0.00, 0.06)

  GW > 12

5229

− 0.04 (− 0.07, − 0.02)

0.002

0.02 (− 0.01, 0.05)

0.13

0.01 (− 0.02, 0.05)

Odds ratio (95% CI)

Odds ratio (95% CI)

Odds ratio (95% CI)

SGA

7637/77,949 (9.8%)

 Any iodine supplement use GW 0–20

28,998

1.01 (0.96, 1.06)

0.83

0.91 (0.87, 0.96)

< 0.001

0.95 (0.88, 1.02)

  Never (non-supplement user)

48,951 (13,393^b)

1 (ref.)

1 (ref.)

1 (ref.)

  Before pregnancy^c

7439

0.97 (0.89, 1.06)

0.49

0.89 (0.82, 0.97)

0.009

0.91 (0.82, 1.01)

  GW 0–12

7121

0.98 (0.90, 1.07)

0.70

0.88 (0.80, 0.95)

0.003

0.91 (0.82, 1.02)

  GW > 12

5229

1.04 (0.94, 1.14)

0.44

0.93 (0.84, 1.02)

0.139

0.95 (0.85, 1.07)

LGA

7539/77,949 (9.7%)

 Any iodine supplement use GW 0–20

28,998

0.92 (0.88, 0.97)

0.002

1.03 (0.98, 1.08)

0.31

1.02 (0.95, 1.10)

  Never (non-supplement user)

48,951 (13,393^b)

1 (ref.)

1 (ref.)

1 (ref.)

  Before pregnancy^c

7439

1.00 (0.92, 1.08)

0.92

1.10 (1.01, 1.19)

0.034

1.08 (0.97, 1.19)

  GW 0–12

7121

0.89 (0.82, 0.97)

0.011

1.03 (0.94, 1.12)

0.57

1.02 (0.92, 1.14)

  GW > 12

5229

0.88 (0.80, 0.97)

0.014

1.01 (0.91, 1.12)

0.89

1.01 (0.90, 1.14)