NEWS

New Research Sheds Light on the Optimal Time for IVF

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Key Takeaways

  • Pinpointing the right time for embryo transfer during IVF remains a challenge.
  • However, researchers have identified a Teflon-like molecule that makes the surface of the womb slippery and prevents embryos from implanting.
  • They believe working around when this molecule is at higher levels can create a “golden window” for pregnancy success.
  • Ultimately, the success of IVF involves several factors, including self-care and trust in your medical team.

The right timing of an embryo transfer is crucial for achieving pregnancy via in vitro fertilization (IVF). This makes it one of the biggest challenges of IVF, too. According to a report from 2018, fewer than 56% of IVF procedures in women ages 35 and under resulted in a live birth. For women ages 42 and older, the success rate was about 4%.

New research from RMIT University in Melbourne, Australia, may help increase the odds. Scientists identified a sticky, Teflon-like molecule that makes the surface of the womb slippery and prevents embryos from implanting. Recognizing when there are higher levels of this molecule in the uterus may make it easier to find the right time for implantation.

The Study

The retrospective clinical study, published in the journal Fertility and Sterility, looked at 81 women who were undergoing IVF treatment. Led by Guiying Nie, PhD, head of RMIT's Implantation and Pregnancy Research Laboratory, the team analyzed levels of podocalyxin (PCX), a sticky molecule that can prevent implantation, in the endometrium (the innermost layer of the uterus).

The researchers found that levels of this molecule on the surface of the uterus decreased at particular points in the menstrual cycle. About seven days after ovulation, in the mid-luteal phase of the menstrual cycle, a biopsy of the uterus was taken. This was done one full menstrual cycle before a frozen embryo was transferred during IVF.

The researchers found that women with low levels of PCX had a 53% pregnancy success rate, while women who did not have lower levels of PCX had a success rate of only 18%.

Guiying Nie, PhD

We know that every embryo is precious for families struggling with infertility, so getting the timing right is critical.

— Guiying Nie, PhD

The researchers believe that low levels of PCX lead to a less sticky womb, which creates an ideal opportunity for pregnancy success.

“To make a baby, you need a good embryo to implant into the wall of a uterus that is ready for pregnancy,” Dr. Nie says. “But we know that the uterus is not suitable for embryo implantation all the time. Our research helps narrow down more precisely to identify that ‘golden window’ when implantation is most likely. We know that every embryo is precious for families struggling with infertility, so getting the timing right is critical.”

Optimizing IVF Success

Carly Snyder, MD, a reproductive and perinatal psychiatrist and Verywell Family review board member, cautions that this study is more relevant for fertility doctors who are developing an IVF plan, rather than patients. “Women can’t regulate or modify their PCX levels,” she points out.

Dr. Nie acknowledges that more research is required and that it is impossible to put a timescale on when a future PCX screening test might be available. “We still need to do more studies to reach a point where our findings can be used directly in the clinic to help patients and physicians,” she says. “We hope with further development our discovery could help clinicians identify precisely when each patient has the greatest chance of achieving pregnancy to deliver fully personalized IVF treatment.”

Carly Snyder, MD

Going through fertility treatments can be very hard, and it’s imperative that women remember to engage in ongoing self care and to keep lines of communication open with their partners, families, and friends.

— Carly Snyder, MD


To optimize the success of IVF and other fertility treatments, Dr. Snyder believes it ultimately comes down to finding the right physician—a professional you trust and have confidence in. Taking care of your body and mind is also crucial.

“Going through fertility treatments can be very hard, and it is imperative that women remember to engage in ongoing self care and to keep lines of communication open with their partners, families, and friends,” Dr. Snyder says. “Struggling with fertility is isolating unless a woman actively lets others in and asks for support as needed.”

What This Means For You

While this information is preliminary, it is another step to increasing the success rates of IVF. If you are thinking about starting IVF, or are preparing for treatment, you may be feeling overwhelmed. Your healthcare provider can help ease your worries by answering any questions you have, including about PCX. If you need emotional or practical support, try to rely on family and friends. IVF can be a long journey, but there are ways to find the support you need.

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2 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Society for Assisted Reproductive Technologies. Final national summary report for 2018. 2018.

  2. Heng S, Samarajeewa N, Aberkane A, et al. Podocalyxin inhibits human embryo implantation in vitro and luminal podocalyxin in putative receptive endometrium is associated with implantation failure in fertility treatment. Fertil Steril. Published online July 13, 2021. doi:10.1016/j.fertnstert.2021.06.028