Table 4.
Summary of evidence of the studies included.
| Authors | Year | Country | Study Design | N | TSH groups | Pregnancy(N) | Delivery(N) | Main finding |
|---|---|---|---|---|---|---|---|---|
| Baker et al. (22) | 2006 | USA | Retrospective Cohort |
364 | ≤2.5mIU/L=72 >2.5mIU/L=92 |
239 76 |
150 45 |
No difference in clinical pregnancy and live delivery |
| Reh et al. (23) | 2010 | USA | Retrospective Cohort | 1055 | ≥2.5 mIU/L=248 <2.5 mIU/L=807 |
128 377 |
97 370 |
No difference in clinical pregnancy and live delivery |
| Michalakis et al. (24) | 2011 | USA | Retrospective Cohort | 1500 | 0.4-2.5 mIU/L=842 2.5–4.0 mIU/L=278 |
368 123 |
295 97 |
No difference in clinical pregnancy and live birth |
| Ding et al. (25) | 2012 | China | Retrospective Cohort | 372 | <2.0 mIU/L=258 2.0-4.5 mIU/L=114 |
78 49 |
– | There was a significant difference in clinical pregnancy rate among the groups. |
| Aghahosseini et al. (26) | 2014 | Iran | Retrospective Cohort | 816 | <2.5mIU/L=487 ≥2.5mIU/L=329 |
131 78 |
– | The risk ratio of negative clinical pregnancy higher in TSH ≥ 2.5 mIU/L |
| Mintziori et al. (27) | 2014 | Greece | Retrospective cohort | 158 | ≤2.5mIU/L=120 >2.5mIU/L=38 |
46 14 |
41 14 |
No difference in clinical pregnancy and live birth rates |
| Karmon et al. (28) | 2015 | USA | Retrospective cohort | 1477 | 0.4-2.49mIU/L=1079 ≥2.5mIU/L=398 |
357 126 |
269 111 |
No difference in clinical pregnancy or live births rates |
| Weghofer et al. (29) | 2015 | USA | Retrospective Cohort | 431 | ≤2.5μIU/mL=330 >2.5μIU/mL=101 |
73 15 |
46 5 |
A trend towards improved pregnancy potential in the presence of TSH ≤ 2.5 mIU/L |
| Coelho-Neto et al. (30) | 2016 | Brazil | Retrospective cohort | 617 | <2.5mIU/L=455 2.5- 4.0mIU/L=162 |
111 42 |
92 36 |
Similar reproductive outcomes, including live birth and clinical pregnancy rates |
| Gingold et al. (31) | 2016 | USA | Retrospective cohort | 1090 | 0.5-2.5mIU/L=773 2.5-5mIU/L=317 |
461 224 |
256 118 |
No difference in the early pregnancy loss rate across in euthyroid patients |
| Tuncay et al. (32) | 2018 | Turkey | Retrospective Cohort | 302 | 0.38–2.49 mIU/L= 233 2.50–4.99mIU/L= 69 |
26 12 |
24 12 |
TSH 2.5 and 4.9 mIU/L do not have a negative effect on clinical pregnancy nor intrauterine fetal death |
| Grove-Laugesen et al. (33) | 2019 | Denmark | Retrospective cohort | 596 | <2.5mIU/L=503 >2.5mIU/L=93 |
22 156 |
20 146 |
TSH level >2.5 mIU/L was associated with lower odds for clinical pregnancy and live birth |
| Turgay et al. (34) | 2019 | Turkey | Retrospective Cohort | 156 | 0.5-2.49 mIU/L=118 2.5-4.5 mIU/L=38 |
18 4 |
14 4 |
No difference live birth, clinical pregnancy and miscarriage rates |
| Jin et al. (35) | 2019 | China | Retrospective cohort | 1185 | ≤2.5mIU/L=830 >2.5mIU/L=355 |
441 175 |
– | No significant effect on the clinical pregnancy rate |
| Zhang et al. (36) | 2020 | China | Retrospective cohort | 1786 | 0.27–2.5 mIU/L=1008 2.5–4.2 mIU/L=778 |
568 452 |
471 385 |
No difference in clinical pregnancy and live-birth |
| Karakis et al. (37) | 2021 | Turkey | Retrospective Cohort | 1465 | 0.27–2.5 mIU/L= 1110 2.51–4.5 mIU/L= 355 |
96 28 |
90 25 |
TSH between 2.5 and 4.5 mIU/L is not associated with lower pregnancy rates or live birth rates |
| Present study | 2022 | Brazil | Retrospective cohort | 256 | 0.5-2.49 mIU/L=211 2.5-4.5 mIU/L=45 |
97 20 |
94 20 |
No difference in clinical pregnancy or live-birth rates |