Advanced Fertility Center of Texas Educates on Single Embryo Transfers

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In honor of National Health Center Week, the health center is offering information about single embryo transfers.

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National Health Center Week is Aug. 10-16, and in honor of the occasion, Advanced Fertility Center of Texas (AFCT) is sharing their expert opinion on single embryo transfers. They explain how during an IVF cycle, the physician and embryologist have to strike a delicate balance between giving a patient the best chance of pregnancy while limiting the chance of multiple pregnancy.

In an ideal world, physicians would like to fertilize only a single egg, transfer a single embryo and have a single baby. This is because a singleton pregnancy gives the best chance of a safe and uneventful pregnancy for the mother and the full-term development for the child.

However, limiting the number of eggs, as has been done in Italy, results in a very low pregnancy rate of some 8 percent per cycle. In other words, only eight couples out of 100 starting an IVF cycle will have a baby. This is about five times lower than in the United States. With such low level of effectiveness, IVF treatment would not be affordable for the majority of couples who need it.

Why does reducing the number of eggs lower the chance of pregnancy?

The answer is as simple as it is vague: not every egg is able to develop to term once fertilized. This phenomenon is called a variation in egg quality. The majority of eggs from an average woman are simply not good enough to produce a viable embryo.

Depending on the woman's age and other factors, the percentage of "good" eggs is between 5 percent and 30 percent. That average, however, has very little practical use, because there are woman with 100 percent good eggs and there those with nearly none.

Egg quality is mysterious. There are no hormones that can be measured and no egg markers to guide us. The only proven way to determine egg quality is to fertilize them (all eggs) and culture them in vitro for five to six days. During such extended in vitro culture, those embryos that are not viable will stop developing, while those that are viable will continue and become a so-called blastocyst by day five or six.

Embryo selection using extended in vitro culture to the blastocyst stage is probably the most important instrument perfected over the last 15 years in an IVF laboratory. Blastocysts can be graded based on their appearance, to further improve the selection process. The chance of a single blastocyst of the excellent quality necessary to become a baby once transferred into the uterus may be as high as 50 percent or even slightly more.

Why only 50 percent?

There are factors other than merely appearance determining embryo viability. Even if an embryo looks normal, it may still have chromosomal errors preventing pregnancy from taking place. Also, chromosomal errors are frequently responsible for a pregnancy loss.

In many cases (but not all), testing for chromosomal errors with PGS (CCS) helps to further narrow down the most viable embryo. Still, even after PGS, the chance of a single embryo to become a baby is probably not higher than 70 percent in the best prognosis patients.

Therefore, no matter how much testing is done on embryos, the current ways to select them remains imperfect and the chances of pregnancy when transferring two or three embryos remain higher than with a single embryo. Physicians must accept, for now, that for most patients they cannot reduce a chance of multiple pregnancy without reducing the chance of pregnancy.

Interestingly, the chance of multiple pregnancy with a single blastocyst transfer is still not zero, because some 5 percent of the blastocysts will split into monozygotic twins. This is a much higher percentage than occurs during a natural conception.

Dr. Michael Allon, medical director, and Dr. Dmitri Dozortsev, laboratory director at Advanced Fertility Center of Texas (AFCT) both encourage those patients who meet the clinical requirements to practice elective single embryo transfer (e-SET). This means that we don't have pre-defined criteria, but rather carefully review the patient's circumstances in its entirety before recommending e-SET.

When there is a possibility of e-SET, it will be discussed with the patient:

1. Woman has a single embryo available
2. At least one excellent blastocyst is available on day five and a woman is under 35 years of age
3. At least one excellent blastocyst is available on day five, it has been tested by PGS and it survived freezing/thawing without any identifiable damage.
4. Woman has some health problems which make multiple gestation pregnancy particularly risky

To learn more, contact AFCT today by calling 713-467-4488 or visiting their website.

About the Center:
Advanced Fertility Center of Texas has several fertility treatment centers located throughout the Houston metropolitan area. They offer the most comprehensive, cutting-edge fertility services available. They assist couples and individuals in experiencing the joy of parenthood, by providing the entire range of fertility services on-site, including artificial insemination, injectable gonadotropins and in vitro fertilization treatment. They have a successful minimal stimulation IVF for poor ovarian reserve patients, egg freezing, egg donor program, fertility preservation and surrogacy. For more information, please visit their website.

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Holly Cordova
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