Improving pregnancy outcomes by genetically screening embryos

This article outlines the current methods available to improve in vitro fertilization (IVF) success rates in women over 35 years old. The authors discuss the outcomes of a single embryo transfer of an embryo that has been genetically selected.

IVF involves the artificial matching of a woman's eggs and the sperm of a male partner/donor in the laboratory. Typically, this process yields several embryos. To ensure a successful pregnancy, several of these embryos are implanted into the uterus at the same time. Unfortunately, this process can increase the risk of having a multiple pregnancy (twins or triplets). A single-embryo transfer (SET – inserting a single embryo into the uterus) dramatically reduces the risk of a multiple pregnancy. In younger women, SET is a viable option resulting in a successful singleton pregnancy and delivery. Older women, however, have significantly lower pregnancy rates following SET.

The present article suggests that women over 35 may also benefit from SET. To achieve this, it is very important to select embryos that are free of any genetic abnormalities. By using a technique called trophectoderm biopsy, it is possible to collect cells for genetic analysis from the embryos without affecting their subsequent development. Recent developments in the field of genetics also allows for a comprehensive chromosome screening (CCS), which checks for all known mutations likely to affect the developing embryo. When used in women over 35, these methods have been found to significantly improve the outcomes of SET. A large trial found that SET following CCS resulted in a 60.8% pregnancy rate compared to 40.9% when using traditional techniques.

Another important development that can help improve SET results in women over 35 is the ability to preserve fertilized embryos as long as needed using special freezing techniques (cryopreservation). Research found that if single embryos were preserved and implanted during periods of increased fertility (as part of the natural menstrual cycle or during controlled hormonal therapy), the pregnancy outcomes were better.

One study found that combining CCS with cryopreservation resulted in a successful pregnancy rate of 56.7% in women over 37 (mean age 40.4 years old).

New developments in IVF techniques seem to improve SET outcomes in women over 35, by better selecting healthier embryos. Improved cryopreservation techniques may help picking the right timing for embryo transfer, thereby improving pregnancy success rates.

It is important to note that these new techniques are not commonly used in practice and can be very costly.

If you are a woman over 35 years old considering IVF, discuss these new advances with your physician to determine if they could be included in your fertility treatment.