Assisted reproductive technologies (ART) have been revolutionizing the fertility industry by offering viable options to infertile couples. In Vitro Fertilization (IVF) is among the most commonly used ART treatments.

IVF involves fertilizing an egg with sperm outside the body and then transferring it to the uterus. Fresh IVF embryos are usually implanted immediately after being fertilized, while frozen embryos are cryopreserved for later use. Historically, doctors have chosen fresh embryos as they believed that they offered higher success rates.

However, recent studies have found that comparing fresh and frozen IVF embryos shows no significant difference in success rates between the two. This article delves into the details of comparing fresh and frozen IVF embryos and examines their success rates.

What are Fresh and Frozen IVF embryos

IVF involves extracting eggs from the female partner and then fertilizing them with sperm in a laboratory dish. The fertilized egg develops into a ball of cells called an embryo.

IVF embryos can be implanted immediately after fertilization (fresh) or cryopreserved for later use (frozen).

Fresh IVF embryos are those that are transferred immediately after being fertilized. For a couple undergoing an IVF treatment cycle, several eggs are extracted and cultured in the laboratory for approximately three to five days.

The embryos that show the best characteristics are selected and transplanted into the woman’s uterus within this period. The remaining embryos are usually frozen for later use.

Frozen IVF embryos, also known as vitrified embryos, are cryopreserved for later use. Cryopreservation is a process that involves rapidly cooling the embryos to very low temperatures (-196°C) and subsequently storing them in liquid nitrogen.

Frozen embryos can be stored for years, and when a patient is ready for transfer, the embryos are thawed and implanted into the uterus.

Comparing Fresh and Frozen Embryos

Historically, doctors chose fresh embryos over frozen ones since they presumed that they offered higher success rates. Fresh embryos are more viable since they have not undergone the stress that comes with cryopreservation.

This reasoning is understandable from a logical standpoint. However, recent studies have found that frozen embryos have similar success rates to fresh ones and, in some cases, are even more advantageous than fresh ones.

A 2018 study by the New England Journal of Medicine compared the birth rates of 800 women who had undergone IVF treatment cycles using either fresh or frozen embryos.

The study found no significant difference in live-birth rates between fresh and frozen embryos. According to the study, approximately 49% of women using fresh embryos, and 50.2% of women using frozen embryos had a live birth.

Furthermore, a 2019 study performed with 34,000 IVF cycles in the U.S. found that good-prognosis patients who underwent a frozen embryo transfer had a higher probability of live birth than patients who underwent a fresh embryo transfer.

Why Frozen Embryos May Be More Advantageous

Frozen embryos have several advantages over fresh embryos, which may contribute to their comparable or even more advantageous success rates. Factors attributed to frozen embryos include:.

1. Allows for More Time to Screen for Chromosomal Abnormalities

Frozen embryos allow doctors to conduct genetic screening tests with greater accuracy and reliability, and more time.

These genetic screening tests evaluate the individual chromosomes in an embryo and can identify numerical abnormalities, such as extra or missing chromosome material. Chromosomal abnormalities can lead to recurrent miscarriages or birth defects.

2. Reduce the Risk of Ovarian Hyperstimulation Syndrome (OHSS)

OHSS is a condition that can arise from stimulating the ovaries to produce multiple eggs, as is the case in IVF treatments. OHSS causes the ovaries to swell, and a patient may experience shortness of breath and intense abdominal pain.

Embryos that remain frozen following an IVF treatment cycle reduce the need for subsequent treatments, with the patient’s ovaries in a hyperstimulated state. As a result, the risk of developing OHSS reduces.

3. Higher Implantation Rates

Embryos sometimes undergo a state of dormancy, during which they do not implant in the uterus. Fresh embryos are implanted during this state, which can lead to a lower implantation rate.

Frozen embryos bypass this stage while in vitro and therefore have a higher chance of implantation in the uterus.

4. Fewer Twin Pregnancies

Transferring several fresh embryos has been the traditional approach to increase the chances of a successful IVF treatment cycle.

However, transferring multiple embryos increases the chances of a twin pregnancy and can lead to complications such as premature births. Frozen embryos allow for single embryo transfers and, therefore, fewer twin pregnancies.

The Cost of IVF Treatment

IVF treatment is an expensive option for couples struggling with infertility. The cost of the treatment varies depending on factors such as egg donor availability, the number of embryos available to freeze, screening tests, and location.

In the United States, the cost of a single cycle of IVF treatment ranges between $12,000 to $25,000.

Many insurance companies do not provide coverage for IVF treatments, thus further straining the financial burden on couples.

However, following the conclusion of the 2018 study comparing fresh and frozen IVF embryos with no significant difference in success rates, insurance companies may give more leeway in the treatments they cover; something that was previously limited specifically to fresh embryo transfers.

Conclusion

For many years, doctors chose fresh embryos, believing that they offered the highest success rates within IVF treatments.

However, recent studies have shown that comparing fresh and frozen IVF embryos shows no significant difference in success rates between the two. In some cases, frozen embryos offer additional and unique advantages that can increase the chances of a successful IVF cycle.

Ultimately, determining whether to use fresh or frozen embryos is a personal choice made between the doctors and their patients, with the patient’s health and financial capacities as the decisive factors.