Considering Assisted Reproductive Technology
In 1978, the world's first "test tube baby" was born after an experimental procedure called in vitro fertilization (IVF) joined a woman's egg and a man's sperm in a glass dish in a laboratory. This was the first time a baby was conceived outside of a woman's body. Since that time, however, millions of babies have been born throughout the world with the help of assisted reproductive technologies (ARTs).
Although ART is a controversial topic for some cultures and religions, the number of people using some type of ART to become pregnant continues to climb. If you have come to the point in your efforts to become pregnant where your healthcare provider may be recommending some type of ART procedure, it's a good idea to become as educated as you can about the various options. Gathering information and understanding the statistics and potential risks can help you and your partner cope with this difficult time and make the decisions that are best for your individual situation.
The Centers for Disease Control and Prevention (CDC) defines assisted reproductive technology as all fertility treatments in which both eggs and sperm are handled. In general, this means that ART procedures involve surgically removing eggs from a woman's ovaries, combining them with sperm in the laboratory, and returning them to the woman's body or donating them to another woman.
The CDC does not include intrauterine insemination (IUI) procedures as an ART process, nor does it include situations in which a woman takes medicine to stimulate egg production without the intent of having eggs retrieved.
ART involves a number of medical treatments that are designed to increase the chance of becoming pregnant. These include:
- In vitro fertilization (IVF)
- Gamete intrafallopian transfer (GIFT)
- Zygote intrafallopian transfer (ZIFT)
- Embryo cryopreservation
- Egg or embryo donation
- Gestational (surrogate) carriers.
An ART procedure may be recommended when other treatments, such as an IUI, have not been successful or when there is severe male factor infertility
, endometriosis, or tubal obstruction.
Each ART cycle consists of multiple steps, and each one occurs at a specific time during a four- to six-week period. Let's break down each one to help identify what's involved.
In Vitro Fertilization
In vitro fertilization is the most commonly used ART procedure, with approximately 99 percent of ART cycles being IVF with embryo transfer. It is a highly complex and meticulously timed procedure. In the most basic terms, this procedure involves:
- Medications (oral and/or injectable) to grow multiple eggs
- Retrieving mature eggs from the woman's ovaries
- Fertilizing the eggs with sperm (insemination)
- Incubating any resulting fertilized eggs (embryos) in a laboratory dish (the resulting embryos are allowed to develop for three to five days before they are transferred into the woman's womb)
- Evaluating the quality and grade of the embryos
- Replacing ("transferring") the selected embryo(s) in the uterus at the appropriate time
- Supporting the uterine lining with hormones needed to sustain pregnancy.
In some cases, additional procedures can be done, such as:
- Intracytoplasmic sperm injection (ICSI) to increase the chance for fertilization. This micromanipulation procedure includes injecting a single sperm directly into an egg to attempt fertilization. It is often used in those with male infertility or in couples with prior IVF failure.
- Assisted hatching (AH) of embryos to increase the chance of an embryo attaching to the uterine wall ("implantation"). This procedure involves partially opening the outer covering (zona pellucida) of the embryo, usually by applying an acid or laser, which helps the embryo attach to the uterine wall.
- Embryo cryopreservation (freezing). This involves freezing the embryos at a very low temperature to keep them viable.
Gamete Intrafallopian Transfer
This particular ART procedure consists of fertilization taking place in the fallopian tube. It is different from IVF in that the unfertilized eggs and sperm are placed together in the woman's fallopian tubes, with fertilization taking place in the fallopian tube instead of a laboratory dish.
The steps involved with a GIFT procedure are similar to IVF, up to the point of egg retrieval. Once the eggs are retrieved from the ovaries, they are immediately transferred into a catheter with the sperm. This catheter is used to place the eggs and sperm into the fallopian tube during a laparoscopy.
Unlike IVF, a GIFT procedure will not include documenting whether fertilization has taken place, nor will it include evaluating the quality of the embryo. A GIFT procedure should only be done when the sperm level is adequate and at least one fallopian tube is open and functional.
Zygote Intrafallopian Transfer
This ART procedure is a combination of IVF and GIFT. It involves transferring a fertilized egg into the fallopian tubes. As with GIFT, the eggs and sperm are mixed together. However, unlike GIFT, the ZIFT procedure consists of fertilization taking place in a laboratory (similar to IVF). The newly fertilized eggs (zygotes) are then transferred into the fallopian tubes. Although fertilization is documented with ZIFT, the dividing embryos are not evaluated as they are with IVF.
Many women who go through IVF will have additional good-quality embryos left over after the procedure. Embryo freezing is an important part of the IVF process. Freezing these embryos, also called cryopreservation, allows them to be used in the future. This cryopreservation provides for a second or third opportunity for pregnancy without having to undergo another ovarian stimulation and retrieval.
The embryos are evaluated based on certain developmental criteria, including appearance and rate of growth. They can be frozen at any of several stages of development. In many cases, the embryos are placed in a cryoprotectant, or antifreeze solution, before being frozen. This solution is made out of sugar and replaces the water within the embryo's cells. This helps protect the cells from forming damaging ice crystals.
There are two methods for freezing embryos, which include:
- Slow cooling: This traditional method consists of placing the embryos into multiple cryoprotectants, added in a specific order, over a 20-minute period. Then, using a computer, the cryoprotectant liquid is slowly cooled until it is frozen. This process takes about two hours and was designed so that the cryoprotectants would infuse into the embryo's cells and protect it from ice. The frozen embryos are then stored in liquid nitrogen (at -196ºC or approximately -400ºF) or in liquid nitrogen vapor.
Although this method is still widely used, it often results in the loss or damage of embryos upon thawing.
- Vitrification: This newer technique involves an ultra-rapid freezing method, in which the embryos are placed into special solutions and then placed immediately into liquid nitrogen. It uses the same principles as the traditional "slow-cooling" method by replacing the water inside the embryo with cryoprotectant. However, instead of a gradual freeze, the embryo is cooled rapidly, which protects the embryo inside the liquid. This process takes approximately one minute.
This final step involves loading the embryo onto a stick and plunging it into liquid nitrogen. Rather than freezing, it is "supercooled" so that the nitrogen becomes solid. The embryo is then suspended in a glass-like bubble of the protective liquid. When the vitrified embryos are thawed, they look nearly identical to when they were fresh.
The method used to freeze embryos dictates how they will be warmed and thawed. Not all embryos will survive the freezing/thawing process. Those that do survive are reassessed. If they have damage that may reduce the chance of implantation, the embryos are not considered viable for transfer.
If you decide to go through an ART procedure, it's important to look at the success rates for the fertility clinics you are considering. The expertise and experience of the lab can make a big difference. Although each facility will have various statistics on success rates, some clinics can have survival rates of up to 95 percent for thawing embryos with the vitrification process, with minimal loss of quality to the embryo.
After thawing, the embryos can be transferred into a woman whose cycle has been synchronized with that of the stage of the frozen embryo.
Embryo or Egg Donation
If you are unable to become pregnant using your own eggs, an egg can be donated by another woman and mixed with your partner's sperm. The resulting embryo can then be implanted in your uterus. This process can also be done with a donated embryo or sperm.
With an IVF procedure, some women create more embryos (fertilized eggs) than they need. The extra embryos can be cryopreserved (frozen) and used for transfer later. However, sometimes couples decide not to use these extra embryos. These people have the option to have their embryos discarded, donated to research, or donated to another woman to achieve pregnancy.
Donated embryos may be considered by those who have:
- Untreatable infertility that involves both partners
- Untreatable infertility in a single woman
- Recurrent pregnancy loss that is believed to be due to the embryo
- Genetic disorders that affect one or both partners.
The U.S. Food and Drug Administration (FDA) has strict guidelines in place to test the people who are donating "tissue," which includes eggs, sperm, and embryos. At the time of donation, the donors should provide a thorough medical history and be tested for communicable diseases, such as hepatitis, syphilis
, and HIV
, just to name a few.
The evaluation of the recipients is similar to that of the people who undergo the IVF procedure. This evaluation includes a detailed medical history, including blood type and Rh factor, and testing for sexually transmitted diseases. It is often recommended that recipients work with a mental health professional regarding the emotional complexity associated with using donor embryos. If the woman is over 45 years old, a more thorough evaluation may need to be done.
Success rates with embryo donation will vary, depending on the quality of the embryos at the time they were frozen, the age of the woman who provided the eggs, and the number of embryos transferred.
A gestational carrier, also known as a gestational surrogate, is when another woman carries your embryo, or a donor embryo, and gives the baby to you after birth. Because the eggs are retrieved from one woman and implanted in another woman, an IVF procedure is required.
Some of the reasons people may choose a gestational carrier include:
- Women who do not have a uterus
- Women who have a medical condition that would prevent carrying a pregnancy safely
- Women who have problems with their uterus that have caused recurrent miscarriage or IVF failure
- Those where a female partner is absent, such as a single male or gay couple.
The gestational carrier should undergo a complete medical history and physical examination to ensure there are no reasons she should not become pregnant. This examination will also include tests to rule out any sexually transmitted diseases. Similar testing and examinations are also done on the intended parents.