Why Aren’t My Embryos Implanting? Understanding Uterine Receptivity

When IVF Doesn’t Work: Why Embryos Sometimes Fail to Implant

If you’ve been through multiple IVF cycles and still haven’t had a successful implantation, you’re not alone. Even when embryos are genetically normal and visually graded as excellent, implantation sometimes fails. It’s a devastating and confusing experience—but it’s also more common than many people realise.

At Acupuncture Pregnancy Clinic, we work with patients who’ve been through this and want real answers. This blog explores the latest evidence about implantation failure, including the critical role of the uterine lining, how Traditional Chinese Medicine (TCM) may help, and six powerful steps to support a more receptive uterine environment.

What the Research Tells Us About Implantation

Even when embryos are screened through Pre-implantation Genetic Testing for Aneuploidy (PGT-A), only around 50% implant and lead to pregnancy. This means uterine receptivity plays a crucial role—it’s not just about embryo quality.

The uterus isn’t a passive container. It’s an active participant in early pregnancy. For implantation to occur, there needs to be a complex conversation between the embryo and the endometrial lining. If the lining isn’t responsive, even a genetically normal embryo may not implant.

Additional Considerations for Implantation Success

While embryo quality is essential, research shows that even genetically normal embryos (PGT-A screened) only implant around 50% of the time in most clinics (Gleicher et al., 2016). This highlights that the receptivity of the uterine environment is just as important as the embryo itself.

Hormonal balance plays a key role in this environment. The interplay between oestrogen and progesterone influences lining thickness, uterine contractility, and immune regulation. For this reason, some IVF clinics recommend frozen embryo transfers (FETs) in natural cycles, where the body’s own hormonal rhythms may offer a more synchronised and receptive window for implantation (Simon & Laufer, 2012).

Emotional stress is another often-overlooked factor. Chronic stress has been shown to increase levels of activated T lymphocytes and Natural Killer (NK) cells, which can shift the immune balance in ways that make implantation less likely (Sacks et al., 2012). It’s not just about feeling calm—stress can actually alter the immune environment of the uterus.

That said, immune cells like NK cells and T cells are not inherently bad—they play a necessary role in early pregnancy. The key is balance. This is an area of ongoing IVF research, and many integrative approaches, including Traditional Chinese Medicine, aim to support immune regulation by nourishing the digestive system and calming the nervous system.

Finally, maternal diet may influence the uterine environment even before implantation occurs. Studies suggest that diets rich in fresh vegetables, fruits, and fish may create a more favourable amino acid profile within the uterus, supporting the development of metabolically “quiet” embryos. Reducing intake of red meat and dairy may also contribute to this shift. The uterus is not just a passive container—it responds to nourishment and care at every stage of the cycle.

Eight Evidence-Informed Factors That Support Uterine Receptivity

1. Tri-laminar Endometrial Pattern
   An ideal endometrial lining shows a tri-laminar (three-line) pattern on ultrasound in the follicular phase. This pattern is associated with higher implantation rates, particularly in frozen embryo transfer cycles. It reflects healthy oestrogen-driven proliferation.
2. Lining Thickness
   Endometrial thickness of at least 6mm is associated with increased implantation rates. Optimal outcomes are often observed when the lining reaches 7–14mm, with adequate vascularisation. Inadequate thickness may reflect hormonal, inflammatory, or circulatory challenges. Often  IVf patients get a measurement of their lining in ultrasounds in the lead up to Embryo transfer. 
3. Uterine Contour and Structural Integrity
   Fibroids, polyps, septa, adhesions, and adenomyosis can physically impede implantation. These may be diagnosed via ultrasound or hysteroscopy. Treatment may include surgical removal, but complementary therapy can support hormonal regulation and inflammation. In terma of Chinese herbal medicine, this can be a good option if the fibroids  or polyps are small. In our clinic we often use  LLLT Laser acupuncture for ( low level light therapy ) for  adhesions, and adenomyosis, as LLLT has in studies shown to influence wounds healing, and inflammation. 
4. Uterine Blood Flow
   Doppler ultrasound studies show that uterine and subendometrial blood flow is a key predictor of implantation success. Acupuncture has been shown in small studies to improve blood flow and reduce uterine artery resistance index, potentially improving receptivity. This why Fertility Acupuncturist at The Acupuncture pregnancy clinic will often suggest acupuncture in the lead up to embryo transfer.
5. Immune System Balance
   The immune environment of the uterus is carefully modulated during implantation. Excessive activity from NK cells or cytotoxic T cells may disrupt this balance. Elevated uterine NK cells and activated T cells can impair implantation. These cells aren’t always “bad”—some are required—it’s about balance. While the science is still emerging, autoimmune issues and chronic inflammation have been associated with implantation failure.
6. Calm Uterine Contractility
   Excessive uterine contractions post-embryo transfer may hinder implantation. A 1998 study in *Human Reproduction* showed implantation rates drop from ~50% to ~10% when uterine contractions exceed five per minute. Acupuncture may assist in calming uterine activity by enhancing parasympathetic tone and this is why IVF acupuncturist at Acupuncture Pregnancy Clinic may suggest post embryo transfer acupuncture.
7. Hormonal Milieu Oestrogen helps build the lining, while progesterone supports implantation and reduces contractions. Disruption to this balance, especially in stimulated IVF cycles, may impact receptivity. This is in part while frozen embryo transfers often achieve better hormonal synchrony.
8. Nutrient-Rich Diet and Amino Acid Profile
   Pre-implantation embryos are sensitive to their chemical environment. Research suggests that maternal diet influences uterine amino acid profiles. Diets rich in fresh vegetables, legumes, and fish are linked to lower amino acid concentrations that may favour the development of metabolically ‘quiet’ embryos. Our Fertility Naturopath offers support around best Fertility nutrition and diet. 

How Acupuncture and TCM May Support Implantation

Traditional Chinese Medicine views the uterus as the ‘palace of the child’. Treatments are tailored to regulate the cycle, nourish ‘Blood’ and ‘Qi’, and calm the mind. Acupuncture has been shown to modulate endometrial receptivity, stress, and blood flow, all of which may support implantation.

Electro-acupuncture in particular has shown promise in improving endometrial thickness and blood perfusion. In one study, acupuncture increased endometrial vascularisation index and implantation rates, although more large-scale trials are needed.

Six Steps to Support Uterine Health

1. Track and regulate your menstrual cycle: A regular cycle reflects healthy ovarian function and hormonal balance. TCM may assist with cycle regulation using acupuncture and herbal medicine.
2. Investigate uterine abnormalities: Ask your fertility specialist to screen for fibroids, polyps, or retained tissue.
3. Support blood flow: Acupuncture, chinese herbs, exercise/ movement, and warm foods can support circulation to the reproductive organs.
4. Manage stress and sleep: Stress may impair immune balance. Acupuncture, mindfulness, and restorative sleep can all help.
5. Focus on a whole-foods diet: Emphasise fresh produce, good fats, and anti-inflammatory foods.
6. Consider immune and hormonal support: Work with your practitioner to assess immune function, and consider TCM herbs where appropriate.

The Role of Natural Killer (NK) Cells

Associate Professor Gavin Sacks has contributed significant research into the role of uterine Natural Killer (NK) cells in implantation failure. While NK cells are a normal part of immune function, elevated levels or activity in the uterus may interfere with successful implantation. Dr Sacks explores immune-modulating treatments and personalised testing to help patients with recurrent IVF failure. We previously worked alongside Dr Gavin Sacks at IVF Australia at Alexandria Specialist Day Hospital and worked closely with Dr Sacks and his patients.  In 2024 ourAlexandria clinic moved into our larger multidisciplinary clinic around the corner from  IVF Australia , but we still have string collaborative relationship. We have helpful resources about Dr gavin Sacks work inot Natural killer cells and also an entertaining  interview where  roles are reversed and Dr Gavin Sacks asks Amy Forth Alexandria Director all about IVF acupuncture.  

To learn more, visit our Q&A with Dr Gavin Sacks (https://acupuncturepregnancy.com.au/q-a-with-dr-gavin-sacks/), his interview with Amy Forth (https://acupuncturepregnancy.com.au/dr-gavin-sacks-ivf-specialist-interviewed-by-dr-amy-forth-acupuncture-pregnancy-clinic-director/), and his own conversation with Amy here (https://acupuncturepregnancy.com.au/turning-the-tables-ivf-specialist-interviews-fertility-acupuncturist/).

Dr Sacks consults through Flow Fertility and IVF Australia. View his full clinical profile here: https://www.ivf.com.au/about-ivf-australia/our-team/ivf-specialists/dr-gavin-sacks

Patient Resources and Next Steps

“Why isn’t it working?” is one of the most heartbreaking and common questions we hear. We want you to know there are supportive strategies, and you’re not alone.

Podcasts we recommend:

– What is Acupuncture? – All About Fertility Podcast: https://podcasts.apple.com/au/podcast/season-1-episode-17-what-is-acupuncture-can-acupuncture/id1508868330?i=1000498735633

– Got Jing? Fertility and Chinese Medicine: https://podcasts.apple.com/us/podcast/got-jing-talking-fertility-acupuncture-chinese-medicine/id1477723922?i=1000476816549

– Can Acupuncture Improve IVF Success?: https://podcasts.apple.com/au/podcast/can-acupuncture-improve-ivf-success-talking-research/id1477723922?i=1000479522547

– Fanny Mechanic x APC Interview: https://www.drandreadis.com.au/Who+is+the+Fanny+Mechanic+%7C+Ep+1

Watch: Embryo implantation animation – YouTube: https://www.youtube.com/watch?v=LxIbFWuDwaE

To book an appointment or learn more about how we support implantation, visit: https://acupuncturepregnancy.com.au

About the Author

This article is authored by Jane Lyttleton, founder of The Acupuncture Pregnancy Clinic (formerly The Acupuncture IVF Support Clinic), established in 2008.

Jane is internationally recognised for her pioneering work in integrative fertility and IVF support. She is the author of the widely referenced text *Treatment of Infertility with Chinese Medicine*, published by Elsevier in 2004 and 2014 and now in its 13th English reprint. Her work forms the basis of the Acupuncture Pregnancy Practice Manual used by APC practitioners.

References

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2. 2. Gleicher N, Kushnir VA, Barad DH. (2016). How PGS/PGT-A laboratories succeeded in losing all credibility. Reproductive Biology and Endocrinology, 14, 1-8.
3. 3. Norwitz ER, Schust DJ, Fisher SJ. (2001). Implantation and the survival of early pregnancy. New England Journal of Medicine, 345(19), 1400–1408.
4. 4. Quenby S, Farquharson R, Young M, Vince G. (2009). Successful pregnancy outcome following diagnosis and treatment of chronic endometritis in women with recurrent miscarriage. Human Reproduction, 17(4), 1067–1071.
5. 5. Sacks G, Yang Y, Sacks R, Kuhn G. (2012). Elevated uterine natural killer cells are associated with reproductive failure: a prospective observational study. Human Reproduction, 27(5), 1226–1234.
6. 6. Simon A, Laufer N. (2012). Assessment and treatment of repeated implantation failure (RIF). Journal of Assisted Reproduction and Genetics, 29(11), 1227–1239.
7. 7. Stener-Victorin E, Waldenstrom U, Andersson SA, Wikland M. (1996). Reduction of blood flow impedance in the uterine arteries of infertile women with electro-acupuncture. Human Reproduction, 11(6), 1314–1317.