Assisted reproductive techniques involve manipulating sperm and eggs or embryos in a laboratory (in vitro) with the goal of producing a pregnancy.
(See also Overview of Infertility.)
If treatment has not resulted in pregnancy after four to six menstrual cycles, assisted reproductive techniques, such as in vitro fertilization or gamete intrafallopian tube transfer, may be considered. These techniques are more successful in women under age 35. For example, in the United States, in vitro fertilization results in the following:
- In women under 35: Live births resulted from about 30% of the procedures.
- In women aged 41 to 42: Live births resulted from only about 11% of the procedures.
For women over 42, using eggs from another woman (donor) is recommended.
Assisted reproductive techniques may result in more than one fetus but are much less likely to do so than fertility drugs.
If the risk of genetic abnormalities is high, the embryo can often be tested before it is implanted in the woman’s uterus. This testing is called preimplantation genetic diagnosis.
Did You Know...
Intrauterine insemination involves selecting only the most active sperm, then placing them directly in the uterus. The most active sperm are selected by washing a semen sample. Doctors try to place these sperm in the uterus at the same time as ovulation.
With this procedure, pregnancy usually occurs by the sixth attempt if it is going to occur. Intrauterine insemination is far less effective than in vitro fertilization but is much less invasive and less expensive.
In vitro (test tube) fertilization (IVF)
In vitro fertilization (IVF) can be used to treat infertility regardless of the cause (including when it is unidentified).
IVF typically involves the following:
- Stimulating the ovaries: Typically, a woman’s ovaries are stimulated with human gonadotropins, with or without clomiphene. A gonadotropin-releasing hormone (GnRH) agonist or antagonist is often given to prevent ovulation from occurring until after several eggs have matured. As a result, many eggs usually mature. Then, human chorionic gonadotropin is given to stimulate ovulation. A GnRH agonist is used to stimulate ovulation in women with a high risk of developing ovarian hyperstimulation syndrome.
- Retrieving released eggs: Guided by ultrasonography, a doctor inserts a needle through the woman’s vagina into the ovary and removes the eggs that have grown and developed (about 34 hours later). Sometimes the eggs are removed through a small tube (laparoscope) inserted through a small incision just below the navel.
- Fertilizing the eggs: The eggs are placed in a culture dish and fertilized with sperm selected as the most active. At this point, a single sperm may be injected into each oocyte (called intracytoplasmic sperm injection), particularly if sperm production is abnormal in the woman's partner.
- Growing the resulting embryos in a laboratory: After sperm are added, the eggs are allowed to grow for about 2 to 5 days.
- Implanting the embryos in the woman’s uterus: One or a few of the resulting embryos are transferred from the culture dish into the woman’s uterus through the vagina. The number of embryos implanted is determined by the woman’s age and likelihood of response to treatment.
More and more often, additional embryos are being frozen in liquid nitrogen to be used later if pregnancy does not occur. Also, practitioners are increasingly doing IVF using only one egg that develops normally during a menstrual cycle (that is, without using fertility drugs).
The chances of having a baby with in vitro fertilization depend on many factors, but the woman’s age may be most important.
The greatest risk of in vitro fertilization is
- Having more than one fetus (multiple pregnancy)
A multiple pregnancy can cause serious complications in the mother and the newborns. Complications may be related to the pregnancy. For example, the mother may develop high blood pressure or diabetes or have excessive bleeding. The fetuses may die, or the babies may have a low birth weight. Because of these complications, doctors now transfer fewer embryos to the uterus at one time.
Birth defects are slightly more common among babies conceived through IVF. However, experts are unclear whether the reason is related to the technique or to the fertility problems that made IVF necessary. Also, more than 6 million babies have been conceived through IVF, and the overwhelming majority of these babies have had no birth defects.
In the United States, the chances of taking home a live baby for each egg retrieved is estimated to be almost 50% for women under age 35 and about 11% for women aged 41 to 42.
Intracytoplasmic sperm injection
Intracytoplasmic sperm injection may be used when
- Other techniques are likely to be unsuccessful.
- A severe problem with sperm is present.
It resembles in vitro fertilization except that only one sperm is injected into each egg.
In 2014, over two thirds of assisted reproductive procedures in the United States involved intracytoplasmic sperm injection.
Birth defects may be more likely after this procedure, possibly because of the following:
- The procedure can damage the egg, sperm, or embryo.
- If sperm from men with an abnormal Y chromosome (one of the sex chromosomes) are used in this procedure, the development of reproductive organs in a male fetus may be affected. Most birth defects in babies conceived by intracytoplasmic sperm injection involve the reproductive organs.
Gamete intrafallopian tube transfer (GIFT)
Gamete intrafallopian tube transfer can be used if the fallopian tubes are functioning normally. Eggs and selected active sperm are obtained as for in vitro fertilization, but the eggs are not fertilized with sperm in the laboratory. Instead, the eggs and sperm are transferred to the far end of the woman’s fallopian tube through a small incision in the abdomen (using a laparoscope) or through the vagina (guided by ultrasonography), so that the egg can be fertilized in the fallopian tube. Thus, this technique is more invasive than in vitro fertilization.
GIFT is rarely used in the United States because IVF is very successful.
These techniques include the following:
- A combination of IVF and GIFT
- Transfer of a fertilized egg (zygote) to the fallopian tube
- Use of eggs from another woman (donor), especially if women are over age 42
- Transfer of frozen embryos to a surrogate mother
These techniques raise moral and ethical issues, including questions about the following:
- Disposal of stored embryos (especially in cases of death or divorce)
- Legal parentage if a surrogate mother is involved
- Use of IVF in postmenopausal women
- Selective reduction of the number of implanted embryos (similar to abortion) when more than three develop
© 2020 Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. Merck Manual Disclaimer