Many factors influence the success of in vitro (IV) fertilization. Among them are the age of the female involved, the age and health of the man who contributes the sperm, the health of the sperm, and the health and viability of the egg. The number of embryos that are transferred, the stimulation used, and laboratory procedures are among the factors that may influence its success as well.
Age is one of the main factors that influences in vitro fertilization success. As a women gets older, her chances of successfully conceiving a child, even with the help of IVF, decline. A woman’s best chances of IVF success are when she is younger than 35. Women who are 35 and above usually have gradually declining success rates. Women who are over 40 years of age typically have the lowest success rates.
Interestingly, the age of the man may also influence IVF success. While a man’s sperm may have the capacity to fertilize an egg well into the man's last decades of life, some studies have produced evidence that male fertility may decline as a man ages. As such, a man who is 40 years old or older may be less fertile than a man in his 20s or 30s.
The health of a woman’s eggs as well as the number of them that are retrieved for fertilization, may also influence IVF success. When a woman’s eggs are healthy, she has a better chance of achieving success through IVF fertilization. She also has a better chance of achieving success on her first attempt than a woman with less-optimal eggs. Likewise, the number of eggs that are retrieved for a procedure influences its success as well. For example, success rates are better when six to 10 eggs are retrieved in comparison to the retrieval of fewer than six eggs; a person may have the lowest expectation of success when fewer than three eggs are retrieved.
Other factors that may influence IVF success rates are medications used to stimulate egg production and laboratory procedures. Hormones are commonly used to stimulate the development of multiple follicles that will release eggs during a cycle. The success of these hormones can dramatically influence the number and health of the eggs that are retrieved. Laboratory factors, such as air quality, light, and temperature may influence IVF success. The efficiency of those performing the lab procedures may affect success rates as well.