Can't get pregnant? What happened to the uterus? Acupuncture improves endometrial receptivity to get pregnant naturally and via IVF.

Endometrial receptivity (ER) refers to the ability of the endometrium, or uterine lining, to accept embryos for implantation, which is a crucial step in achieving pregnancy. ER undergoes changes throughout the menstrual cycle, and there are only a few days when the uterine lining is optimal for embryo implantation. This timeframe, known as the implantation window, typically occurs 6-10 days after ovulation, which falls between the 20th and 24th day of a normal menstrual cycle.

Research has indicated that a thin endometrium is closely associated with a low pregnancy rate. When the average size of follicles reaches 18 mm and the endometrial thickness is less than 7.0 mm, embryo implantation is greatly affected. While higher-quality embryos are typically selected for transfer in in vitro fertilization-embryo transfer (IVF-ET) cycles, only a few of them successfully implant. Studies have shown that up to 75% of pregnancy losses can be attributed to implantation failure, with two-thirds of IVF-ET implantation failures being linked to low endometrial receptivity.

Therefore, improving endometrial receptivity is crucial for achieving natural pregnancy or increasing the success rate of IVF-ET. A thin endometrium is one of the most significant factors contributing to low ER, where it is defined as a thickness of less than 7.0 mm during the middle luteal phase (after ovulation) between days 6 and 10. Research has demonstrated a close relationship between low pregnancy rates and a thin endometrium. When the average size of follicles reaches 18 mm and the endometrial thickness is less than 7.0 mm, embryo implantation is greatly affected. Clinical studies have shown that an endometrial thickness of more than 8 mm is more favorable for successful embryo implantation and development. Endometrial thickness, pattern, and blood supply are closely associated with embryo implantation. Studies suggest that increasing uterine blood flow and endometrial thickness positively impact ER and enhance the implantation and clinical pregnancy rates in IVF-ET cycles.

Although significant advancements have been made in embryo quality, little progress has been achieved in improving the poor quality of ER over the past three decades since the introduction of IVF. Acupuncture, as a non-drug therapy, has been chosen by many infertile couples as a treatment option.

Can acupuncture improve endometrial receptivity?
A recent study conducted a thorough analysis of randomized controlled trials (RCTs) to examine the potential of acupuncture in improving endometrial receptivity (ER). The analysis included a total of 3041 patients. The findings of the study indicated that there is some evidence suggesting that acupuncture might enhance the pregnancy rate, embryo transfer rate, and endometrial thickening.

In another recent review, researchers examined the data from 14 trials involving 1564 women participants. The review spanned from the inception of the trials up until 26 February 2022, and its objective was to explore the dosage-dependent effectiveness of acupuncture in improving endometrial receptivity.

The results of this review revealed that receiving acupuncture treatment for only 2 or 4 days did not lead to improvements in uterine blood flow, endometrial receptivity, or pregnancy rates. However, when acupuncture treatment was administered for an entire menstrual cycle, significant improvements were observed in uterine blood flow, endometrial thickness (the lining of the uterus), endometrial receptivity, and there was a higher pregnancy rate compared to the control group.

Furthermore, the review found that when acupuncture treatment was continued for three menstrual cycles, even greater enhancements in uterine blood flow, endometrial thickness, endometrial receptivity, and pregnancy rates were observed compared to the control group.

Based on the evidence from the reviewed studies, it appears that acupuncture may have a positive impact on endometrial receptivity. Longer durations of acupuncture treatment, such as a full menstrual cycle or three cycles, seem to yield more significant improvements in uterine blood flow, endometrial thickness, and pregnancy rates when compared to shorter treatment durations. However, it is important to note that further research is needed to fully understand the mechanisms and effectiveness of acupuncture in improving endometrial receptivity.

Xiaoyan Zheng, et al Front Public Health. 2022; 10: 858587
Yajing Zhong et al BMC Complement Altern Med. 2019; 19: 61.

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