JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):233
Poster Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263848

P-221. The association between thyroid autoimmune diseases and embryo implantation failure in women undergoing assisted reproductive techniques: a narrative review

Luna Decultot¹, Drielly dos Reis Franzoi¹, Endjeli Vogler Reche¹, Maria Mônica Pereira¹

¹ Centro Universitário São Camilo - São Paulo – SP - Brasil

Objective: To evaluate the association between thyroid autoimmune diseases (TAI) and embryo implantation failure in women undergoing assisted reproductive techniques.
Methods: A systematic narrative review was conducted based on studies indexed in the Medline (via PubMed) and LILACS (via BVS) databases, published in the last ten years, using terms related to assisted reproductive techniques and thyroid diseases, yielding 49 articles. Selection was performed in a blinded manner by two independent reviewers through the Rayyan platform, with a third reviewer resolving any conflicts. Eligible articles were organized in a table and read in full by all authors. Studies involving pregnant women with TAI that included analyses of implantation rates, clinical pregnancy, or live birth rates were included.
Results: Ten studies were included: six historical cohort studies, two prospective cohorts, two multicenter retrospective cohorts, and one non-randomized controlled clinical trial. Most indicated that the presence of TAI, even in euthyroid women with subclinical hypothyroidism (SCH), is associated with poorer reproductive outcomes. One cohort of 589 women showed that the TAI group had a lower implantation rate than the non-TAI group, whereas another cohort with 1,031 participants found no such difference. In the first study, there were no significant differences in embryo characteristics or pregnancy outcomes, such as antral follicle count, normal fertilization rate in in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI), number of high-quality embryos, clinical pregnancy rate, miscarriage rate, and live birth rate; however, in the second study, the biochemical pregnancy rate was significantly lower in the TAI group. Studies comparing clinical pregnancy or live birth rates found that one, involving 1,400 women, reported lower clinical pregnancy rates in those with TAI compared to those without TAI; another, with 1,578 participants, showed that women with TSH ≥ 2.0 mIU/L and TPOAb ≥ 30 U/mL had a reduced live birth rate (RR=47.7); another study with 270 euthyroid participants with SCH showed no statistically significant difference in clinical pregnancy rates between women with TSH 0.2-2.5 and those with TSH 2.5-4.2. Regarding secondary outcomes, one study found a significantly higher miscarriage rate in patients with TAI, with no differences in the number of pregnancies. A controlled clinical trial found that titrating levothyroxine based on frequent TSH monitoring in women with SCH during IVF cycles did not result in significant differences in clinical pregnancy and live birth rates compared to no levothyroxine use. These results suggest that maintaining TSH below 2.5 mIU/L before IVF does not influence reproductive outcomes. In addition, two studies showed that adjuvant treatment with prednisone and aspirin in euthyroid women with TAI undergoing IVF did not significantly improve implantation, clinical pregnancy, live birth, or miscarriage rates. Regarding differences between women undergoing IVF or ICSI, with and without TAI, one study showed that ICSI had higher overall fertilization rates; however, among patients with TAI, ICSI was associated with lower live birth and clinical pregnancy rates.
Conclusion: The presence of TAI appears to be associated with poorer reproductive outcomes in women undergoing assisted reproduction, even in those who are euthyroid. This was observed in several stages of the reproductive process, including embryo quality, implantation rate, clinical pregnancy, and live birth rates, as well as an increased risk of pregnancy loss. These findings highlight the importance of early identification and management of TAI as a potential strategy to improve outcomes in assisted reproductive techniques.