Effects of acupuncture on the pregnancy outcomes of frozen-thawed embryo transfer: A systematic review and meta-analysis

Infertility has become an increasingly common problem, affecting millions of couples worldwide. For many women facing difficulties conceiving, frozen-thawed embryo transfer (FET) represents an important treatment option within assisted reproductive technologies. This procedure is especially useful for women who have had previous cycle cancellations or implantation failures and who have at least one viable frozen embryo. Although FET has demonstrated significant advantages, such as a reduced risk of ovarian hyperstimulation syndrome, clinical pregnancy rates still remain around 58.7%, which has motivated researchers and clinicians to seek complementary therapies that can improve these outcomes.

Acupuncture, one of the oldest practices of Traditional Chinese Medicine, has gained growing interest as an adjunctive treatment for women undergoing FET. Studies suggest this therapy may act on the neuroendocrine-immune system, improving endometrial receptivity and reducing adverse reactions during the embryo transfer process. However, research findings on the efficacy of acupuncture in FET have been controversial and conflicting, with some studies showing significant benefits while others find no statistically important differences. This lack of scientific consensus has generated uncertainty for both healthcare professionals and patients considering including acupuncture in their treatment protocols.

Given this controversy, Chinese researchers conducted a comprehensive systematic review with meta-analysis to rigorously evaluate the effects of acupuncture as adjunctive treatment in women undergoing FET. The primary objective of the study was to determine whether acupuncture can improve clinical pregnancy rates, defined as the presence of at least one gestational sac with fetal heartbeat confirmed by ultrasound five weeks after transfer. As secondary objectives, the researchers evaluated biochemical pregnancy rates, live birth rates, endometrial thickness, and endometrial pattern. The methodology rigorously followed international guidelines for systematic reviews, including only randomized clinical trials comparing acupuncture with sham acupuncture or no adjunctive treatment.

The researchers conducted comprehensive searches in multiple medical databases, including PubMed, Cochrane Library, and Chinese databases, covering studies from inception through June 2022.

The results of the analysis were promising and statistically significant for several important outcomes. Fourteen randomized clinical trials with a total of 1,130 participants were included, all conducted in China. For the clinical pregnancy rate, the primary outcome assessed, acupuncture showed a significant beneficial effect, with a 54% greater probability of achieving clinical pregnancy compared with control groups. Biochemical pregnancy rates were also favorable, with a 51% increase in the probability of a positive pregnancy test.

In addition, acupuncture demonstrated positive effects in improving endometrial receptivity, increasing endometrial thickness by nearly 1 mm on average and promoting the endometrial pattern most favorable to implantation, known as the trilaminar pattern. Although live birth rates showed a positive trend, this result did not reach statistical significance, possibly due to the small number of studies reporting this specific outcome. Regarding safety, only four studies reported adverse events, all mild in nature such as nausea or dizziness, with no serious adverse events related to acupuncture treatment.

The clinical implications of these findings are important for both clinicians and patients. For women undergoing FET, these results suggest that acupuncture may be a safe and potentially effective complementary therapeutic option to improve their pregnancy chances. The therapy proved especially beneficial for specific populations, including women with recurrent implantation failure, polycystic ovary syndrome, and women over 35. For healthcare professionals, the data provide scientific evidence that can support patient counseling on complementary treatment options.

The study also revealed important information about the most effective acupuncture protocols, suggesting that sessions performed before or during the FET period, with at least 5 treatment sessions, tend to produce better results. The analysis showed that true acupuncture treatments were more effective than untreated control groups, while studies comparing with sham acupuncture showed less conclusive results, possibly because sham acupuncture may also have some therapeutic effect.

Nevertheless, it is essential to acknowledge important limitations of this study that should be considered when interpreting the results. The methodological quality of the included studies varied considerably, with many studies not providing adequate information on randomization, allocation concealment, or blinding of assessors. All studies were conducted in China, which may limit the generalizability of results to other populations and healthcare systems. The analysis also identified possible publication bias, suggesting that studies with negative results may not have been published with the same frequency.

Heterogeneity among studies regarding acupuncture protocols, number of sessions, treatment timing, and patient characteristics also represents an important limitation. In addition, the quality of evidence was rated as low to moderate by rigorous international criteria, indicating that true effects may be substantially different from the estimates presented.

In conclusion, although this study provides encouraging evidence on the potential of acupuncture as adjunctive therapy for FET, with demonstration of significant benefits in clinical pregnancy rates and improved endometrial receptivity, the results should be interpreted with caution due to the methodological limitations identified. Acupuncture proved to be a safe therapy with minimal risk of serious adverse events, which is reassuring for patients considering this option. Going forward, studies of higher methodological quality are needed, with larger samples, standardized acupuncture protocols, and ideally involving populations from different countries and cultural contexts to confirm these promising findings and establish more precise guidelines on when and how to use acupuncture in the context of assisted reproduction.