One of the most common reasons that an embryo transfer does not result in a pregnancy is due to abnormal embryo genetics. Carrier screening is a type of testing used to assess genetic risks to a patient/couple’s offspring that would not be evident just from personal or family history alone. The genetic conditions we look for through carrier screening are called recessive disorders, where both copies of the gene have to be no longer working properly in order for an individual to actually show symptoms of that condition.
In some cases, both members of a couple may be carriers for a recessive genetic condition such as cystic fibrosis or sickle cell anemia.
Carrier screening also typically looks for common X-linked conditions, which are conditions that only females (individuals with two X chromosomes) carry such as Fragile X syndrome. It is completely normal to be a carrier; most people carry one or more recessive conditions and are asymptomatic. However, if a carrier has a child with someone who also carries the same condition, then there is a significant risk (25%) of having a child with that genetic disease.
If both members of a couple are found to be carriers of the same disease, or a female carrier for an X-linked disease, it is possible through in vitro fertilization (IVF) to screen embryos via pre-implantation genetic testing (PGT) and determine before pregnancy is attempted whether or not each embryo is predicted to be affected with the genetic disorder. Only embryos that are not affected with the condition are transferred back into the uterus to attempt pregnancy.
Even if a couple elects to undergo IVF without PGT, there are a few helpful considerations such as being aware that additional prenatal testing is indicated. In some cases, preparing a special pediatric care team to be ready after birth. Carrier screening is used to assess genetic risks that would not be evident from personal or family history alone. Carrier screenings look for recessive disorders, where both copies of the gene are no longer working properly in order for an individual to actually show symptoms of that condition.
During an IVF cycle, eggs are retrieved from the female patient and fertilized with sperm in the IVF laboratory. The embryos created are allowed to develop for 5-7 days until they reach the blastocyst stage of development.
The embryologist takes a small sample of cells from the outer layer of the blastocyst. This outer layer will later develop into the placenta and other supporting structures of the pregnancy.
PGT testing takes 1-2 weeks for the results to come back. Your doctor will review the results with you to help choose which embryo to use for transfer. Some embryos are then chosen for a frozen embryo transfer cycle to be scheduled at a later time.