In vitro fertilization (IVF) is currently the most effective treatment available for infertility of nearly all causes. It is a very precise and controlled process, which involves stimulating the growth of multiple eggs, removal of the eggs from the ovaries (egg retrieval), fertilization in the embryology laboratory, and subsequent placement of the best-quality embryos into the uterus (embryo transfer). Despite continuing improvements in the technology, unfortunately there are times when IVF is not successful on the first or second try. While the devastation that often accompanies a negative pregnancy test after IVF is completely natural, it is important to understand why it is that IVF pregnancy rates are not 100% and why, in most cases, you should consider trying again.
When an IVF cycle is not successful, the most common reason is that the embryo(s) stop growing before they can implant. Other possible factors to be considered include the uterine receptivity and the mechanics of the embryo transfer, but the large majority of unsuccessful IVF cycles can be attributed to embryo quality.
When we speak of embryo quality, we are referring to the ability of the embryo to continue growing and to “stick” once it is inside the uterus. To some degree, this can be predicted by the appearance of the embryos prior to the transfer. All embryos are assigned grades based on their rate of development and some more subjective features such as symmetry of cells and degree of fragmentation.
Embryos with high quality grades are more likely to implant than those with low quality grades, but sometimes even the most perfect-looking embryo does not implant. What could possibly explain this? The answer comes from decades of clinical experience, which has consistently shown that the factor that best predicts whether a woman will become pregnant after IVF is the quality of the eggs which produced the embryos. Other important components include the quality of the sperm and the quality of the embryology laboratory (for example, culture conditions and expertise of the embryology staff vary from lab to lab), but the quality of the eggs is without a doubt the most important as it is the responsibility of the egg to ensure a normal chromosomal complement in the embryo.
Egg quality is primarily determined by a woman’s age, but can vary from month to month since, at the beginning of each menstrual cycle, a woman has a different “batch” of eggs that can potentially be utilized for IVF. Egg quality can also be influenced by decisions made by your IVF doctor, such as the choice of ovarian stimulation protocol, the choice of hormone medications to achieve follicle growth, and the timing of the ovulation trigger. Because of the normal cycle-to-cycle variability in egg quality and the ability to modify the ovarian stimulation based on what was learned from the previous IVF attempt(s), in most cases, IVF is worth trying again.
Within each age group, the chance of pregnancy from IVF is the same for the first 3-4 attempts, and though it decreases a little thereafter, we continue to see pregnancies in patients even on their fifth or sixth attempt. In fact, a recent study reported that, in patients undergoing up to six cycles of IVF, the probability of eventually having a baby was excellent (up to 86% for women < 35, and up to 42% for women over 40).
Comments are closed.