What is IVF Natural Transfer?

We developed and have been using Natural Transfer™ treatment cycle since 2014.


In the recent past, the freezing of embryos created during IVF was unreliable and many embryos did not survive after the thawing process. Therefore, physicians were under pressure to transfer the best embryos immediately after ovarian stimulation to avoid the need for freezing. As a result, the best embryos were transferred into the uterus after they had been exposed to large amounts of hormones, which reduced the ability to accept embryos for implantation. In the past few years, the embryos are frozen with a process called vitrification, which allows for 99% of our embryos to survive the thawing process and be used for transfer. Because  the embryos were transferred during ovarian stimulation, the uterus was not at the optimal condition to accept the embryos. Factors like fluid in the cavity, a thin uterine lining, or high progesterone levels may impact the success of embryo implantation.

In natural transfer, there is reduced hormonal exposure to the uterus and the uterus is optimized prior to embryo transfer.

With natural transfer, we can also minimize the risks of ovarian hyperstimulation and ectopic pregnancy.

How Does IVF Natural Transfer Work?

Thanks to a breakthrough in embryo freezing called vitrification, embryos can now be cryopreserved without significant risk of damaging them in the process.

AFCT has always been at the forefront of new developments in clinical embryology and became one of the first IVF programs in the United States to adopt vitrification for embryos and egg freezing to all our patients.

AFCT uses a proprietary vitrification protocol, which has been perfected by our laboratory director, Dr. Dmitri Dozortsev.

Vitrification uses an extremely high cooling speed that prevents the formation of ice crystals, which are damaging to the embryo. Unlike automated, programmed freezing, vitrification relies heavily on the expertise and skills of the operator. Therefore, it takes time to perfect the process.

As a result, all AFCT patients have their best embryos transferred into the uterus during what AFCT calls “Natural Transfer”, where they are welcomed by the uterus in a perfect state for implantation.

Why Choose IVF Natural Transfer?

There are several reasons for improved outcomes with a natural transfer:

With ovarian stimulation and the growth of the oocytes (eggs), estrogen levels increase to 10-20 times higher than normal in a natural cycle. The high estrogen levels have a negative effect on the uterus by causing it to become out of sync with the growth of the eggs. High estrogen levels inhibit the effects of progesterone, which is the most essential hormone in the process of implantation and pregnancy.

Women with the diagnosis of polycystic ovarian syndrome (PCOS) naturally have a higher number of eggs compared to other patients. The higher number of eggs will lead to very high levels of estrogen by the end of IVF stimulation.

The risk of ovarian hyperstimulation syndrome, a medical condition that can occur when a woman takes medication to stimulate egg growth, increases with high estrogen levels. This is even more common in patients with PCOS, who may experience severe abdominal discomfort, fluid collection in the abdomen, and shortness of breath, which may require hospitalization. When we perform frozen embryo transfer, we can alter the stimulation protocol and almost completely eliminate the risks associated with this syndrome.

Since 2014 and the introduction of the Freeze All approach, AFCT has maintained phenomenally high pregnancy rates, which were recently verified by the CDC.

Several studies confirm the theory that we can obtain significantly higher pregnancy rates when we wait and transfer the embryos in a frozen cycle. A major advantage of freezing embryos is that they can be safely stored until a woman’s normal hormonal balance is restored, which makes the uterus more receptive to implanting an embryo.

“Natural Transfer™” can provide the highest chance of pregnancy with the lowest complications associated with ovarian stimulation. Published data shows that infants born after the transfer of vitrified embryos in non-stimulated cycles are about 150 grams bigger, and the mothers have a lower risk of premature labor.

Dr. Michael Allon, Board Certified Reproductive Endocrinologist and a Medical Director of AFCT: “It is difficult to exaggerate the significance of Natural Transfer™ IVF success. Miraculously, we see that not only does this new approach drastically increase the chances of pregnancy, but it also diminishes the difference in outcomes between older and younger patients.”