Levothyroxine in pregnancy
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Levothyroxine in Pregnancy: Effects on Pregnancy Outcomes
Introduction to Levothyroxine and Pregnancy
Levothyroxine (LT4) is a synthetic form of the thyroid hormone thyroxine, commonly prescribed to manage hypothyroidism. During pregnancy, maintaining optimal thyroid function is crucial for both maternal health and fetal development. This article synthesizes research findings on the impact of LT4 supplementation on pregnancy outcomes, particularly in women with subclinical hypothyroidism (SCH) and thyroid autoimmunity (TAI).
Levothyroxine and Pregnancy Loss
Subclinical Hypothyroidism and Pregnancy Loss
Research indicates that LT4 supplementation significantly reduces the risk of pregnancy loss in women with SCH. A meta-analysis of 13 studies involving 7970 women found that LT4 decreased the pregnancy loss rate (PLR) by 44% in women with SCH 1. Another study focusing on women undergoing assisted reproduction technologies (ART) reported a similar reduction in miscarriage rates with LT4 treatment 3.
Thyroid Autoimmunity and Pregnancy Loss
Women with TAI also benefit from LT4 supplementation. The same meta-analysis showed a 37% reduction in pregnancy loss among women with TAI 1. Additionally, a study on infertile women undergoing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) found that LT4 significantly decreased miscarriage rates in this group 2.
Levothyroxine and Preterm Birth
Subclinical Hypothyroidism and Preterm Birth
The effect of LT4 on preterm birth rates in women with SCH is less clear. While some studies suggest a reduction in preterm birth rates, the evidence is not statistically significant. For instance, a meta-analysis found no significant reduction in preterm birth rates among women with SCH treated with LT4 1.
Thyroid Autoimmunity and Preterm Birth
In contrast, LT4 supplementation appears to be more effective in reducing preterm birth rates in women with TAI. The same meta-analysis reported a 32% reduction in preterm birth rates among women with TAI 1. Another study confirmed these findings, showing that LT4 treatment lowered the risk of preterm delivery in TPOAb-positive women 8.
Levothyroxine and Assisted Reproduction Technologies
Impact on IVF/ICSI Outcomes
For women undergoing ART, LT4 supplementation has shown mixed results. A meta-analysis of randomized controlled trials (RCTs) found no significant improvement in clinical pregnancy rates, live birth rates, or preterm birth rates with LT4 treatment. However, it did significantly reduce miscarriage rates 2. Another study supported these findings, showing that LT4 treatment improved delivery rates and reduced miscarriage rates in women with SCH undergoing ART 3.
Levothyroxine in Euthyroid Women with Thyroid Autoimmunity
General Pregnancy Outcomes
The benefits of LT4 supplementation in euthyroid women with thyroid autoimmunity are less conclusive. A systematic review and meta-analysis found no significant improvement in live birth rates, miscarriage rates, or preterm birth rates with LT4 treatment in this group 45. Another study echoed these findings, showing no significant differences in pregnancy outcomes between LT4-treated and untreated euthyroid women with TPO antibodies 6.
Conclusion
Levothyroxine supplementation appears to offer significant benefits in reducing pregnancy loss and, to a lesser extent, preterm birth rates in women with subclinical hypothyroidism and thyroid autoimmunity. However, its benefits in euthyroid women with thyroid autoimmunity are less clear. Further large-scale, high-quality RCTs are needed to confirm these findings and provide more definitive guidance on the use of LT4 in pregnancy.
Sources and full results
Most relevant research papers on this topic
Effect of levothyroxine supplementation on pregnancy loss and preterm birth in women with subclinical hypothyroidism and thyroid autoimmunity: a systematic review and meta-analysis
Levothyroxine supplementation significantly decreases pregnancy loss and preterm birth risks in women with subclinical hypothyroidism and thyroid autoimmunity.
Meta-Analysis
Very Rigorous Journal
Highly CitedEffect of levothyroxine supplementation on pregnancy outcomes in women with subclinical hypothyroidism and thyroid autoimmuneity undergoing in vitro fertilization/intracytoplasmic sperm injection: an updated meta-analysis of randomized controlled trials
Levothyroxine supplementation may reduce miscarriage rates in infertile women with subclinical hypothyroidism and thyroid autoimmuneity undergoing IVF/ICSI, but more population-based RCTs are needed to confirm this recommendation.
Meta-Analysis
Rigorous JournalLevothyroxine treatment and pregnancy outcome in women with subclinical hypothyroidism undergoing assisted reproduction technologies: systematic review and meta-analysis of RCTs.
Levothyroxine supplementation can improve clinical pregnancy outcomes in women with subclinical hypothyroidism and/or thyroid autoimmunity undergoing assisted reproduction technologies.
Meta-AnalysisHighly CitedEffect of levothyroxine on pregnancy outcomes in women with thyroid autoimmunity: a systematic review with meta-analysis of randomized controlled trials.
Levothyroxine supplementation is not associated with improved pregnancy outcomes in women with thyroid autoimmunity.
Meta-AnalysisLevothyroxine in Women with Thyroid Peroxidase Antibodies before Conception
Levothyroxine treatment in euthyroid women with thyroid peroxidase antibodies did not result in a higher rate of live births compared to placebo.
RCT
Large Human TrialRigorous JournalHighly CitedLevothyroxine Supplementation in Euthyroid Pregnant Women With Positive Autoantibodies: A Systematic Review and Meta-Analysis
Levothyroxine supplementation in pregnant euthyroid women with TPO antibodies does not reduce the risk of pre-term birth in TPO-positive women with normal thyroid function.
Meta-AnalysisThe impact of levothyroxine therapy on the pregnancy, neonatal and childhood outcomes of subclinical hypothyroidism during pregnancy: An updated systematic review, meta-analysis and trial sequential analysis
Levothyroxine therapy showed no significant benefit on pregnancy, neonatal, and childhood outcomes in pregnant women with subclinical hypothyroidism.
Meta-AnalysisEffects of levothyroxine treatment on pregnancy outcomes in pregnant women with autoimmune thyroid disease.
Levothyroxine treatment decreases the risk of preterm delivery in pregnant women with autoimmune thyroid disease, but without overt thyroid dysfunction.
RCTLarge Human TrialRigorous JournalHighly CitedImpact of levothyroxine in women with positive thyroid antibodies on pregnancy outcomes: a systematic review and meta-analysis of randomised controlled trials
Levothyroxine use in pregnant women with thyroid autoimmunity shows no significant benefit in terms of pregnancy outcomes, miscarriage, preterm delivery, or live births.
Meta-AnalysisRigorous JournalPregnancy and Neonatal Outcomes With Levothyroxine Treatment in Women With Subclinical Hypothyroidism Based on New Diagnostic Criteria: A Systematic Review and Meta-Analysis
Levothyroxine treatment in pregnant women with subclinical hypothyroidism may reduce the risk of pregnancy loss, preterm delivery, and gestational hypertension.
Meta-Analysis