Levothyroxine and the risk of adverse pregnancy outcomes in women with subclinical hypothyroidism
PubMed Central: Published February, 2021
Subclinical hypothyroidism (SCH) is
a common biochemical entity identified in women during pregnancy. SCH is
diagnosed when the thyroid stimulating hormone (TSH) is elevated with a normal
free thyroxine (FT4) level.
The thyroid hormone, FT4, is
necessary for fetal growth and development. Insufficient thyroid hormone has
been shown to impair fetal growth and brain development and it may have negative
effects on neonatal survival.
Women with overt hypothyroidism
during pregnancy require levothyroxine treatment. There is well-established
evidence for the need to treat women with overt hypothyroidism during pregnancy
as studies have shown that untreated hypothyroidism during pregnancy leads to an increased risk of pregnancy complications, including increased risks of preterm
birth, low birth weight, and stillbirth
However, there is uncertainty as to
whether women with SCH during pregnancy should be treated as the benefits of
treating SCH during pregnancy have not been consistently demonstrated.
Although most women with SCH are asymptomatic, previous studies have shown that SCH may be associated with adverse outcomes during pregnancy.
TAKE HOME MESSAGE:
The aim of this study is to conduct
a systematic review and meta-analysis to examine the risk of adverse pregnancy,
perinatal, and early childhood outcomes among women with SCH treated with
levothyroxine.
In this systematic review and
meta-analysis, the authors assessed the available evidence regarding the use of
levothyroxine in treating SCH during pregnancy. Authors found that the use of
levothyroxine among women with SCH was associated with a decreased risk of
pregnancy loss and neonatal death relative to non-use.
Although available data are
limited, there is also evidence that levothyroxine treatment is associated with
improved fetal outcomes, including reductions in fetal distress and macrosomia.
Conclusion
This systematic review and meta-analysis found that, compared with
non-use, treatment of Subclinical hypothyroidism (SCH) with levothyroxine
during pregnancy is associated with decreased risks of pregnancy loss and
neonatal death.
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Background
Levothyroxine replacement therapy
may decrease the risk of adverse pregnancy outcomes among women with
subclinical hypothyroidism (SCH). The aim of this study is to conduct a
systematic review and meta-analysis to examine the risk of adverse pregnancy, perinatal,
and early childhood outcomes among women with SCH treated with levothyroxine.
Methods
A systematic literature search was
conducted using Ovid-Medline, Ovid-EMBASE, Pubmed (non-Medline), Ebsco-CINAHL
Plus with full text and Cochrane Library databases. Randomized controlled
studies (RCTs) and observational studies examining the association between
treatment of SCH during pregnancy and our outcomes of interest were included.
Studies that compared levothyroxine treatment versus no treatment were eligible
for inclusion. Data from included studies were extracted and quality assessment
was performed by two independent reviewers.
Results
Seven RCTs and six observational
studies met our inclusion criteria. A total of 7342 individuals were included
in these studies. RCTs demonstrated several sources of bias, with lack of
blinding of the participants or research personnel; only one study was fully
blinded. In the observational studies, there was moderate to serious risk of
bias due to lack of adjustment for certain confounding variables, participant
selection, and selective reporting of results. Pooled analyses showed decreased
risk of pregnancy loss and neonatal death associated with levothyroxine
treatment during pregnancy among women with SCH. There were no associations
between levothyroxine treatment and outcomes during labour and delivery, or
cognitive status in children at 3 or 5 years of age.
Conclusion
Treatment of SCH with levothyroxine
during pregnancy is associated with decreased risks of pregnancy loss and
neonatal death. Given the paucity of available data and heterogeneity of
included studies, additional studies are needed to address the benefits of
levothyroxine use among pregnant women with SCH.
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