Assisted Reproductive Technology

Assisted Reproductive Technology

What is Assisted Reproductive Technology (ART)?

Although various definitions have been used, ART includes all fertility treatments in which both eggs and sperm are manipulated. In general, ART involves 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. It does NOT include procedures in which only sperm are manipulated (i.e., artificial insemination or intrauterine insemination) or procedures in which a woman takes drugs only to stimulate egg production, without the intention of having eggs retrieved.

The types of ART include:

IVF (In Vitro Fertilization).
GIFT (Gamete Intrafallopian Transfer).
ZIFT (Zygote Intrafallopian Transfer).
TET (Tubal Embryo Transfer)

In addition, ART is often categorized according to whether the procedure used a woman's own eggs (nondonor) or eggs from another woman (donor) and according to whether the embryos used were newly fertilized (fresh) or previously fertilized, frozen, and then thawed (frozen).

ART Types

IVF (in vitro fertilization) involves extracting a woman's eggs, fertilizing the eggs in the laboratory, and then transferring the resulting embryo(s) into the woman's uterus through the cervix.
GIFT (gamete intrafallopian transfer) involves using a fiber-optic instrument called a laparoscope to guide the transfer of unfertilized eggs and sperm (gametes) into the woman's fallopian tubes through small incisions in her abdomen.
ZIFT (zygote intrafallopian transfer) involves fertilizing a woman's eggs in the laboratory and then using a laparoscope to guide the transfer of the fertilized eggs (zygotes) into her fallopian tubes.Most IVF, GIFT, and ZIFT cycles used fresh, nondonor eggs or embryos.

What are the causes of infertility among couples who use ART?

Figure 6 shows the primary diagnoses reported for infertility among couples who had an ART procedure in 1997. Although some couples have more than one cause of infertility, only one is reported as primary. In addition, diagnostic procedures and categories may vary from one clinic to another, so the categorization may be inexact.

Tubal factor usually means that the woman's fallopian tubes are blocked or damaged, making it difficult for the egg to be fertilized or for an embryo to travel to the uterus.
Male factor usually refers to a low sperm count or problems with sperm function that make it difficult for a sperm to fertilize an egg under normal conditions.
Endometriosis involves the presence of tissue similar to the uterine lining in abnormal locations. This condition can affect both egg fertilization and embryo implantation.
Ovulatory dysfunction means that the ovaries are not producing eggs normally or that egg production has diminished with age.
Unexplained cause means that no cause of infertility was found in either the woman or the man.
Other causes of infertility include immunological problems, chromosomal abnormalities, cancer chemotherapy, and serious illnesses.
Uterine factor means a disorder of the uterus that results in reduced fertility.

Does the cause of infertility affect the chances of success using ART?

Figure 14 shows the percentage of live births after an ART procedure according to the primary cause of infertility. (See the glossary for an explanation of the diagnoses.) The success rates varied little among most of the different diagnoses; most were near the overall national success rate of 24.0%. However, the use of these diagnostic categories may vary from clinic to clinic, and the definitions are imprecise.

Do ART success rates differ among women of different ages?

A woman's age is the most important factor affecting the chances of a live birth when her own eggs are used. Figure 11 shows both the pregnancy and live birth rates for women of different ages who had ART procedures in 1997. Among women in their twenties, both pregnancy and live birth rates were relatively stable; however, both rates declined sharply from the mid-thirties onward as fertility declined with age.

Figure 4 presents 1997 ART cycles using fresh, nondonor eggs or embryos according to the age of the woman who had the procedure. About 70% of these cycles were among women aged 30-39. Because very few women younger than age 22 used ART and very few women older than age 47 used ART with their own eggs, those cycles are not included in the figure.