Levothyroxine and pregnancy side effects
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Levothyroxine and Pregnancy Side Effects
Introduction to Levothyroxine and Pregnancy
Levothyroxine (LT4) is a synthetic form of the thyroid hormone thyroxine, commonly prescribed to manage hypothyroidism. During pregnancy, maintaining appropriate thyroid hormone levels is crucial for both maternal health and fetal development. However, the use of levothyroxine in pregnant women, particularly those with subclinical hypothyroidism (SCH) or thyroid autoimmunity (TAI), has been a subject of extensive research due to its potential impact on pregnancy outcomes.
Impact on Pregnancy Loss and Preterm Birth
Subclinical Hypothyroidism (SCH)
Research indicates that pregnant women with SCH are at a higher risk for adverse outcomes such as pregnancy loss and preterm birth. A meta-analysis found that levothyroxine supplementation significantly decreased the pregnancy loss rate (PLR) and preterm birth rate (PBR) in women with SCH and/or TAI . However, another study highlighted that while levothyroxine reduced the risk of pregnancy loss, it did not significantly affect the rate of preterm birth in women with SCH .
Thyroid Autoimmunity (TAI)
For women with TAI, levothyroxine supplementation has shown to reduce both pregnancy loss and preterm birth rates. This effect was more pronounced in naturally conceived pregnancies compared to those achieved through assisted reproduction technologies (ART) . Another study confirmed these findings, showing that levothyroxine treatment in TAI-positive women decreased the risk of preterm delivery and miscarriage .
Effects on Maternal and Neonatal Outcomes
General Pregnancy Outcomes
The impact of levothyroxine on broader pregnancy outcomes remains mixed. Some studies suggest that levothyroxine therapy does not significantly improve outcomes such as gestational hypertension, preeclampsia, or gestational diabetes in pregnant women with SCH Jiao2022Maraka2016. However, other research indicates that levothyroxine may reduce the risk of gestational hypertension and improve overall pregnancy outcomes when diagnosed using the most recent criteria .
Neonatal Outcomes
Levothyroxine treatment has been associated with a decreased risk of neonatal death among women with SCH . However, there is no consistent evidence that levothyroxine improves other neonatal outcomes such as birth weight or Apgar scores .
Assisted Reproduction Technologies (ART)
In the context of ART, levothyroxine supplementation has been shown to improve clinical pregnancy outcomes and reduce miscarriage rates in women with SCH and/or TAI . However, the benefits of levothyroxine in ART settings are less clear for other outcomes like preterm delivery and gestational hypertension, indicating a need for further research .
Controversies and Recommendations
Despite the potential benefits, the use of levothyroxine in pregnant women with SCH or TAI remains controversial. Some studies argue that there is insufficient evidence to support routine levothyroxine therapy for improving pregnancy outcomes in these populations Jiao2022Lau2021. The variability in diagnostic criteria and study methodologies contributes to these conflicting findings.
Conclusion
Levothyroxine supplementation in pregnant women with subclinical hypothyroidism or thyroid autoimmunity can reduce the risk of pregnancy loss and preterm birth, particularly in naturally conceived pregnancies. However, its impact on other maternal and neonatal outcomes is less clear, and further research is needed to establish definitive guidelines. Clinicians should consider individual patient profiles and the latest diagnostic criteria when prescribing levothyroxine during pregnancy.
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