In vitro fertilization (IVF) is a process by which egg cells are fertilized in vitro, that is, by sperm outside of the womb. IVF is a major treatment in infertility when other methods of assisted reproductive technology have failed. Assisted reproductive technologies (ART) include multiple techniques that allow gamete manipulation outside the body and have evolved greatly over the past 2 decades.
IVF involves egg retrieval from the ovary, fertilization in the laboratory (fluid medium), and replacement of the zygote in the patient's uterus. The first live birth resulting from this technique occurred in June 1978. Since then, over 1 million children have been born throughout the world with the use of assisted reproduction.
Assisted reproductive techniques have been used for more than 20 years, reporting an increasing number of cycles treated, an increasing pregnancy rate, and an increase in live births per cycle (from 6.6% in 1985 to 27% in 2006) for IVF. In 2003 there were 122,872 ART cycles (99.4% were IVF cycles), whereas in 2006, 41,343 live-birth deliveries were reported; approximately <1.0% were gamete intrafallopian transfer for fertilization (GIFT) and <1.0 % accounted for zygote intrafallopian transfer (ZIFT) cycles. In approximately half of the ART cycles (53%), intracytoplasmic sperm injection (ICSI) is used.
One of the most important prognostic predictors for pregnancy is the age of the female partner. Whereas for women younger than 35 years, live birth rate/cycle varies from 30 to 35%, women older than 40 years face live birth rates <6%, down to 2.4%. Table 57–1 presents data according to the National Summary and fertility reports of the US Department of Health and Human Services.
Table 57–1. In Vitro Fertilization. ||Download (.pdf)
Table 57–1. In Vitro Fertilization.
|Cycles performed in relation to age groups|
|<35 y||35–37 y||38–40 y||>40 y|
|Number of cycles performed||54,386||31,127||25,933||26,752|
|Outcomes according to age groups|
|<35 y||35–37 y||38–40 y||41–42 y|
|% cycles resulting in pregnancy||45.2||37.7||23.5||19.0|
|% cycles resulting in live births||37.4||31.1||20.6|
|Average number of embryos transferred||2.0||2.5||3.8||2.9|
|% of twin gestation||38.5||12.5|
|% of cancellations||12.2||6.6||13.2|
Approximately 39% of patients who undergo egg retrieval will become pregnant with sonographic documentation of an intrauterine pregnancy (clinical pregnancy); 82% of these patients will carry to term. Many "biochemical pregnancies" occur, but these should not be included in pregnancy statistics. A biochemical pregnancy is one in which serum levels of human chorionic gonadotropin (hCG) rise and then fall before sonographic detection of pregnancy is possible. Eggs are almost always obtained by aspiration, and under ordinary circumstances, approximately 75% of eggs will fertilize and cleave. The clinical pregnancy rate of approximately 34% per embryo transfer per IVF cycle (women <35 years old) is > 20–25% pregnancy rate per cycle observed in spontaneous conceptions in the general population.