One of the first questions that most people ask is “what is the chance for success?” In 2002 about 28% of cycles in the United States in which women underwent IVF and embryo transfer with their own eggs resulted in the live birth of at least one infant. This rate has been improving slowly but steadily over the years. Patients should be aware, however, that some clinics define “success” as any positive pregnancy test or any pregnancy, even if miscarried or ectopic. These “successes” are irrelevant to patients desiring a baby. To put these figures into perspective, studies have shown that the rate of pregnancy in couples with proven fertility in the past is only about 20% per cycle. Therefore, although a figure of 28% may sound low, it is greater than the chance that a fertile couple will conceive in any given cycle.
Success varies with many factors. The age of the woman is the most important factor, when women are using their own eggs. Success rates decline as women age, and success rates drop off even more dramatically after about age 37. Part of this decline is due to a lower chance of getting pregnant from ART, and part is due to a higher risk of miscarriage with increasing age, especially over age 40. There is, however, no evidence that the risk of birth defects or chromosome abnormalities (such as Down’s syndrome) is any different with ART than with natural conception.
Success rates vary with the number of embryos transferred. However, transferring more embryos at one time not only increases the chance of success with that transfer, but will also increase the risk of a multiple pregnancy, which are much more complicated than a singleton pregnancy. The impact of the number of embryos that are transferred on success rates also varies with the age of the woman.
Pregnancy complications, such as premature birth and low birth weight, tend to be higher with ART pregnancies, primarily because of the much higher rate of multiple pregnancies. Nationally, in 2002-2003 about 30% of ART deliveries were twin deliveries, versus 1-2% of spontaneous pregnancies. The risk of pregnancy containing triplets or more was 6% in 2003.
As women get older, the likelihood of a successful response to ovarian stimulation and progression to egg retrieval decreases. These cycles in older women that have progressed to egg retrieval are also slightly less likely to reach transfer. The percentage of cycles that progress from transfer to pregnancy significantly decreases as women get older. As women get older, cycles that have progressed to pregnancy are less likely to result in a live birth because the risk for miscarriage is greater. This age related decrease in success accelerates after age 35 and even more so after age 40. Overall, 37% of cycles started in 2003 among women younger than 35 resulted in live births. This percentage decreased to 30% among women 35–37 years of age, 20% among women 38–40, 11% among women 41–42, and 4% among women older than 42. The proportion of cycles that resulted in singleton live births is even lower for each age group.
The success rates vary in different programs in part because of quality, skill and experience but also based on the above factors of age, number of embryos transferred and patient population. Patients may also differ by diagnosis and intrinsic fertility which may relate to the number of eggs a patient may be able to stimulate reflected by baseline FSH and antral follicle count as well as the genetics of their gametes. These differences make it impossible to compare programs.
Another factor often overlooked when considering one’s odds of conceiving and having a healthy baby from an IVF procedure is the success with cryopreserved embryos.
Thus, a program which may have a lower success rate with a fresh transfer but much higher success with a frozen embryo transfer will result in a better chance of conceiving with only a single IVF stimulation and retrieval. Success with frozen embryos transferred in a subsequent cycle also allows the program to transfer fewer embryos in the fresh cycle minimizing the risk of a riskier multiple pregnancy. It may be more revealing to examine a program’s success with a combination of the fresh embryo transfer and frozen embryo transfers resulting from a single IVF stimulation and transfer. For example, at East Coast Fertility, the combined number of fresh and frozen embryo transfers that resulted in pregnancies from January 1, 2005 to April 2006 was. The number of retrieval during that time was. The success rate combining the fresh and frozen pregnancies divided by the number of retrievals was 77.2%. The high frozen embryo transfer pregnancy rate allowed us to transfer fewer embryos so that there were 0 triplets from fresh transfers during this time.
What can I do to increase my odds?
Patients often ask if there are any additional procedures we can do in the lab that may improve the odds of conception. Assisted hatching is the oldest and most commonly added procedure aimed at improving an embryo’s ability to implant. Embryos must break out or hatch from their shell that has enclosed them since fertilization prior to implanting into the uterine lining. This can be performed mechanically, chemically and most recently by utilizing a laser microscopically aimed at the zona pellucidum, the shell surrounding the embryo. Assisted hatching appears to benefit patients who are older than 38 years of age and those with thick zonae.
Recently a protein additive called “Embryo glue” was shown to improve implantation rates in some patients whose embryos were transferred in media containing “Embryo glue”. Time will tell if the adhesive effect of this supplement is truly increasing success rates and warrants wide scale use in IVF programs.
Embryo co culture is the growth of developing embryos is the same Petri dish as another cell line. Programs utilize either the woman’s endometrial cells obtained from a previous endometrial biopsy or granulosa cells obtained at the time of the egg retrieval from the same follicles aspirated as the eggs. Growth factors produced by these endometrial and granulosa cell lines diffuse to the developing embryo and are thought to aid in the growth and development of the embryo. It appears to help patients who have had previous IVF failures and poor embryo development.