Abstract
ObjectiveStudies have shown a high incidence of subclinical hypothyroidism in pregnancy, but the adverse pregnancy outcomes caused by it are not clear. Therefore, we conducted a systematic review and meta-analysis to evaluate the relationship between subclinical hypothyroidism in pregnancy and hypertensive disorders of pregnancy(HDP) to guide clinical practice.MethodWe searched the MEDLINE (PubMed), Cochrane Central, EMBASE, Web of Science, and SCOPUS databases and screened all studies evaluating the relationship between subclinical hypothyroidism in pregnancy and hypertensive disorders of pregnancy. Two researchers independently evaluated the quality of all eligible original studies using the Newcastle-Ottawa Scale (NOS). We also performed a meta-analysis using STATA15.1. Sensitivity analyses were also performed by examining the effects of individual studies as well as using different effect models and detecting any publication bias using the harbord test.ResultsTwenty-two studies were included in the final meta-analysis. Our results indicated that pregnant women with subclinical hypothyroidism had an increased risk of HDP (OR = 1.54(95% CI: 1.21-1.96) I²=67.1%), compared with euthyroidism. Subclinical hypothyroidism in pregnancy was not associated with hypertensive disorders of pregnancy at TSH diagnostic cut-off of less than 3.0 mIU/L (P = 0.077). Curiously, the risk of HDP increases when the TSH diagnostic cut-off value is higher or lower than 4 mIU/L. Although only 9 studies were above the threshold, the risk of developing HDP was still 1.69 times, which was highest in all subgroup analyses. This is consistent with the newly recommended diagnostic cut-off value of 4 mIU/L for TSH by the ATA. Our results consider that the risk of hypertensive disorder complicating pregnancy is increased regardless of the diagnosis of subclinical hypothyroidism at any stage of pregnancy. Unfortunately, there is insufficient evidence to support that patients can benefit from treatment with levothyroxine.ConclusionThe results of this meta-analysis indicate that subclinical hypothyroidism in pregnancy is associated with an increased risk of developing HDP, and this association exists regardless of the gestational period. However, the available evidence cannot support these patients receiving thyroxine intervention can benefit from it, so routine screening is only recommended for pregnant women with risk factors for hypothyroidism. Further research is needed to validate more scientific and rigorous clinical studies to clarify the relationship between subclinical hypothyroidism and HDP to improve patient prognosis.Systematic Review Registration https://www.crd.york.ac.uk/prospero/, PROSPERO (CRD42021286405)
Highlights
As one of the most important endocrine diseases in pregnant women, thyroid disease during pregnancy has gradually become a hot spot in clinical and basic research in the field of maternalfetal medicine with the publication of the results of more than ten large-sample clinical trials in recent years
We further searched the full texts of 40 articles to assess their eligibility, of which 15 were case-control studies, 2 studies were poorly defined for disease, and 2 studies that did not provide HDP-related data were excluded
The results showed that when the diagnostic cut-off value of TSH was less than 3 mIU/L, subclinical hypothyroidism in pregnancy was not associated with HDP, and when it was more than 3 mIU/L, the risk of HDP increased by 1.67 times
Summary
As one of the most important endocrine diseases in pregnant women, thyroid disease during pregnancy has gradually become a hot spot in clinical and basic research in the field of maternalfetal medicine with the publication of the results of more than ten large-sample clinical trials in recent years. Subclinical hypothyroidism as a population with a large number of patients has attracted countless attention. HDP is one of the important causes of maternal and neonatal-perinatal death and other serious adverse pregnancy outcomes worldwide and has been a focus of attention for clinicians for many years because of its wide range of effects as well as high medical expenditure. A variety of studies have investigated the relationship between maternal subclinical hypothyroidism and a variety of obstetric as well as neonatal outcomes including HDP [4–7]. Some existing clinical studies have conflicting conclusions and no uniform consensus has been reached
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
