Embryo

Preimplantation genetic testing (PGT) is the general term for genetic testing performed on embryos produced by in vitro fertilization (IVF) before the embryos are transferred to the uterus. The purpose of PGT is to improve the chances of having a successful embryo transfer.

Genetic testing does not impact or change the genetics of an embryo, but it does give doctors and prospective parents more information and may help them select the most viable embryos for transfer.  

There are three types of PGT: PGT for monogenic disorders (PGT-M), PGT for structural chromosomal rearrangements (PGT-SR), and PGT for aneuploidy (PGT-A). PGT-A is the most routine type performed and as such should be understood by prospective parents.

An embryo transfer is usually the final step in the process of in vitro fertilization (IVF), where the embryo is transferred to the patient’s uterus. The embryos used in this procedure may either be fresh or thawed (after being frozen).

During IVF, mature eggs are fertilized, either by conventional IVF (insemination) or intracytoplasmic sperm injection (ICSI), after which the resulting embryos are grown in an incubator in the embryology laboratory. An embryo transfer is the procedure whereby one or more of the embryos that has been grown in the lab setting is then transferred from culture media into the patient’s uterus, in the hopes of initiating a pregnancy.  

Fresh embryo transfers are those in which the embryo was fertilized after the ovarian hyperstimulation and egg retrieval process, then transferred in the same cycle. As such, the embryo has never been frozen.ⁱ

Alternatively, embryos can be frozen and preserved by a process called cryopreservation, and then stored to be transferred in a subsequent cycle. This is known as a frozen embryo transfer (FET) and requires the cryopreserved embryo to be thawed before transferring into the uterus.ⁱⁱ

There has been a significant increase in the number of frozen embryo transfer cycles being performed in the last decade due to better cryopreservation techniques, improvement in embryo culture media, providers choosing the “freeze-all” strategy to avoid ovarian hyperstimulation syndrome, more patients undergoing embryo banking for fertility preservation or family planning, and advancements in preimplantation genetic testing.ⁱⁱⁱ

After an egg retrieval for a fresh cycle, or when contemplating a frozen embryo transfer, women often wonder how many embryos should be placed into the uterus. Usually, single embryo transfer (SET) is promoted, especially if an embryo is genetically tested (undergoes pre-implantation genetic testing, PGT). However, there are cases where a patient may want to transfer two or more embryos. Examining the pros and cons of multiple embryo transfer can help women make an informed decision.

Chromosomes are made up of DNA and genes that determine multiple aspects of a human’s makeup. Chromosome analyses are often performed in an attempt to give a healthcare provider more insight into a range of issues, from potential genetic conditions to what may be causing recurrent miscarriage. Embryonic and fetal genetic testing may be recommended or pursued for a variety of reasons. Sometimes, individuals or couples have genetic conditions that run in their families, in which case in vitro fertilization (IVF) with preimplantation genetic testing (PGT) can help select embryos that do not carry this condition. In other cases, those attempting to conceive or who have had multiple pregnancy losses may pursue genetic testing of an embryo to help ascertain a cause. Genetic testing can also give an early glimpse into the sex of the fetus as well as whether the fetus has extra/missing chromosomes that could cause conditions such as Down or Turner Syndromes.

A dilation and curettage (D&C) is a surgical procedure that is used to remove tissue from the uterus, and while it is performed for a variety of reasons including diagnostic purposes, it is typically used following a miscarriage or for elective termination of a pregnancy. An understanding of what to expect before, during, and after a D&C is beneficial for navigating this procedure, as well as to learn about potential risks and alternative treatments.

Preimplantation genetic testing (PGT) is the general term for genetic testing performed on embryos produced by in vitro fertilization (IVF) before the embryos are transferred to the uterus. The purpose of PGT is to improve the chances of having a successful embryo transfer.

Genetic testing does not impact or change the genetics of an embryo, but it does give doctors and prospective parents more information and may help them select the most viable embryos for transfer.  

There are three types of PGT: PGT for monogenic disorders (PGT-M), PGT for structural chromosomal rearrangements (PGT-SR), and PGT for aneuploidy (PGT-A). PGT-A is the most routine type performed and as such should be understood by prospective parents.

Read through the different stages of embryo development and what happens after egg retrieval in IVF. Day-by-day outlines and more from researchers in the field.

Conceiving through in vitro fertilization (IVF), or other assisted reproductive technology, is a multifaceted process that involves several steps. Once eggs have been retrieved, successfully fertilized, and the embryos have developed, the embryo transfer procedure is planned by the reproductive endocrinologist (REI, also called RE). IVF embryo transfer processes vary depending on factors that include whether fresh or frozen embryos are used and how many embryos are planned for transfer. Successful embryo implantation into the uterine cavity requires careful planning before the actual transfer procedure itself, and possibly a few lifestyle adjustments for the woman during the weeks immediately following the procedure.

In order to increase the chances of a successful pregnancy, embryo grading is completed by an embryologist during an in vitro fertilization (IVF) cycle. Assessing embryos for quality at specific stages of embryo development can be a valuable tool in reproductive medicine to help the doctor decide which embryo to transfer first (when there is more than one embryo available for transfer). Understanding what takes place during embryo grading is important, in that it can help patients determine what their next steps in the IVF process might be.

Preimplantation genetic testing (PGT) is the general term for genetic testing performed on embryos produced by women undergoing in vitro fertilization (IVF) before transfer to the uterus. PGT aims to improve the chances of having a successful ongoing pregnancy after embryo transfer. While genetic testing does not impact or change the genetics of an embryo, it gives doctors and prospective parents more information and may help them select the most viable embryos for transfer.