Table 5 Maternal TH levels

0.300–4.5 IU/L

1.10–2.50 nmol/L

60–140 nmol/L

–

1st Trimester

2nd-3th Trimester

1st Trimester

2nd-3th Trimester

[38]

Kato

Japan

2016

Median week: 11.1

392

TSH (mIU/L)*

1.0

LOD-4.1^a

FT4 (pmol/L)*^{, d}

12.7

7.9–21.56 ^a

[39]

Preston

USA

2018

<14th week. (1st trimester)

732

TSH (mIU/mL) ^e

1.2

< 0.01–21.4

TT4 (nmol/L)*

127.4

50.2–314.1

Positive (> 2 U/mL): 14%

FT4Index

2.1

1.3–6.0

[40]

Inoue

Denmark

2019

Week 5–19 (Median week 8) (1st Trimester)

1366

TSH (mIU/L)

1.13^b

1.08–1.19 ^a

FT4 (pmol/L)

14.2^b

14.1–14.3 ^a

[41]

Wang

Norway

2013

Week 17–18 (2nd trimester)

903

TSH (mIU/L)

3.52

Max: 18.64

[42]

Webster

Canada

2014

Week 15 (2nd trimester)

150

TSH (mIU/L)

1.3

0.0–3.3

TT4 (nmol/L)

126.4

77.4–200.1

High (≥ 9 IU/mL): 9%

FT4 (pmol/L)

9.5

7.3–12.9

Week 18 (2nd trimester)

TSH (mIU/L)

1.3

0.2–4.0

TT4 (nmol/L)

119.1

65–7-175.7

FT4 (pmol/L)

8.5

5.8–11.1

[43]

Berg

Norway

2015

2nd trimester (week 13–28)

375

TSH (mIU/L)

1.55

0.06–10.2

TT3 (nmol/L)

2.71

1.47–4.75

TT4 (nmol/L)

145

92.00–215

Positive (>  34 IU/L): 6%

FT3 (pmol/L)

4.59

2.99–7.08

FT4 (pmol/L)

13.0

9.00–20.0

3 days postpartum

372

TSH (mIU/L)

2.37

0.15–9.51

TT3 (nmol/L)

2.75

1.32–4.66

TT4 (nmol/L)

144

77.0–232

Positive (>  34 IU/L): 4%

FT3 (pmol/L)

4.50

2.72–6.77

FT4 (pmol/L)

13.0

8.00–19.0

6 weeks postpartum

374

TSH (mIU/L)

1.39

0.06–6.54

TT3 (nmol/L)

1.70

1.15–2.53

TT4 (nmol/L)

97.0

63.0–153

Positive (>  34 IU/L): 4%

FT3 (pmol/L)

4.63

3.14–6.48

FT4 (pmol/L)

14.0

10.0–25.0

[44]

Wang

Taiwan

2014

Week 28–40 (3rd trimester)

274–285

TSH (mIU/L)

1.76

TT3 (nmol/L)*

2.45

TT4 (nmol/L)*

143.7

FT4 (pmol/L)*

7.3

[45]

Reardon

Canada

2019

<  13 weeks

167

TSH (mIU/L)*^{, e}

1.18

0.15–3.21^c

FT3 (pmol/L)

4.62

3.72–5.58 ^c

FT4 (pmol/L)

14.9

11.8–19.6 ^c

High (>  9 IU/mL): 5%

14–26 weeks

487

TSH (mIU/L)*^{, e}

1.38

0.57–3.25 ^c

FT3 (pmol/L)

4.53

3.69–5.51 ^c

FT4 (pmol/L)

14.0

11.6–17.5 ^c

High (>  9 IU/mL): 15%

27–40 weeks

465

TSH (mIU/L)*^{, e}

1.28

0.52–2.45 ^c

FT3 (pmol/L)

4.36

3.62–5.41 ^c

FT4 (pmol/L)

12.6

10.0–16.6 ^c

High (>  9 IU/mL): 15%

3 months postpartum

479

TSH (mIU/L)*^{, e}

1.14

0.07–2.28 ^c

FT3 (pmol/L)

4.13

3.30–5.30 ^c

FT4 (pmol/L)

14.0

11.6–19.4 ^c

High (>  9 IU/mL): 14%

[46]

Yang

China

2016

1–2 days before delivery (3rd trimester)

123–157

TSH (mIU/L)

3.03

0.26–12.77

TT3 (nmol/L)

2.54

0.77–3.86

TT4 (nmol/L)

140.00

71.42–288.30

FT3 (pmol/L)

3.82

1.76–5.41

FT4 (pmol/L)

11.89

7.45–17.49

[47]

Xiao

Faroe Island

2019

Week 34 (3rd Trimester)

172

TSH (mIU/L)*^{, f}

1.34^b

0.23–3.61

FT3 (pmol/L)

4.25 ^b

2.94–6.62

TT4 (nmol/L)

121.08 ^b

61.00–224.00

T3RU

0.66 ^b

0.51–1.01

FT4 (pmol/L)

8.18 ^b

5.49–14.70

FT4Index (IU/L)

80.47 ^b

53.00–164.00