Table 5.
Maternal TH levels
| Reference | Author Country Year |
Time point of TH measurement | TSH | T3 | T4 | TPOAb | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Number | Median | Range | Median | Range | Median | Range | |||||||
| Normal range in non-pregnant women# | 0.300–4.5 IU/L | 1.10–2.50 nmol/L | 60–140 nmol/L | – | |||||||||
|
Normal range in pregnant women American Thyroid Association |
1st Trimester | Upper reference limit of 4.0 mU/L | |||||||||||
| 2nd-3th Trimester | Gradually return to non-pregnancy range | ||||||||||||
| European Thyroid Association | 1st Trimester | Upper reference limit of 2.5 mU/L | |||||||||||
| 2nd-3th Trimester | Upper reference limit of 3.0 mU/L | ||||||||||||
| Studies included in review | |||||||||||||
| [38] |
Kato Japan 2016 |
Median week: 11.1 | 392 | TSH (mIU/L)* | 1.0 | LOD-4.1a | 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) | 1.13b | 1.08–1.19 a | FT4 (pmol/L) | 14.2b | 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 | 0.15–3.21c | 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 | 1.34b | 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 | |||||||||||
TT3 (total triiodothyronine), FT3 (free triiodothyronine), TT4 (total thyroxine), FT4 (free thyroxine), T3RU (Free triiodothyronine resin uptake), *: Converted values, for TSH all values are converted to mIU/L, for TT3 and TT4 all values are converted to nmol/L, for FT3 and FT4 all values are converted to pmol/L, a: 95% confidence interval, b: Geometric mean, c: Range defined as the 5th percentile and 95th percentile of the sample population, d: In the article the value reported were 0.99 ng/mL, converted to pmol/L giving 1274.3 pmol/L; other FT4 values from the same cohort (Minatoya et al. 2017) have reported similar values in ng/dL. We believe that the correct unit is 0.99 ng/dL (=12.7 pmol/L), which gives normal FT4 levels, e: Values were reported as mIU/mL in tables, however other places in the article the more used μIU/mL or IU/L were used, we choose to interpret the values as μIU/mL as the values are in the normal range and comparable with values reported from other studies. f: Values were reported as IU/L, we choose to interpret the values as μIU/mL / mIU/L as the values are then in the normal range and comparable with values reported from other studies. #: Aarhus University Hospital, Aarhus, Denmark