What does the success of an IVF cycle depend on?
To achieve a pregnancy, the elements needed are: an egg, a spermatozoon and a receptive endometrium in an adequate uterus.
However, the success of the fecundation process depends on a few factors:
When the ovarian puncture is performed, it is uncommon for all the retrieved eggs to be of high quality. The most common situation is to find a few mature oocytes, others that are non-viable and yet others that despite being mature will not be fecundated. The number of good quality oocytes will be determined by the patient’s age as well as her lifestyle.
It is also important to realize that although there are millions of spermatozoa in an ejaculation, not all of them are good. It is the spermiogram that will reveal whether the sample has the characteristics to yield the desired result. An IVF treatment will be very effective, for example, in the case of low sperm motility, as it is more difficult for the sperm to get to the egg in a natural setting than with an insemination.
When the sperm fertilizes the egg an embryo is created. In the In Vitro Fertilization process, the embryo stays in the lab for 2, 3 or 5 days, where it is observed and graded by category, ranging from poor to excellent quality. The higher the quality of the embryo, the more likely it is to implant. Also, the more advanced the development of the embryo, the more information we will have about its quality. The ideal transfer day is either on day 3 or day 5 of the embryo’s development, in order to select the best embryos.
It is extremely important to choose a fertility clinic with a lab that can offer the most advanced techniques. The lab plays a very important role in the sperm selection and at the time of fecundation, because the embryos are kept in an incubator. Without strict controls in lab protocol, the embryos could suffer environmental stress that could halt their development.
The embryo or embryos that are obtained will be transferred via the uterine cavity, at the endometrium level. It is essential to prepare the endometrium to ensure the success of an IVF treatment. The uterus is evaluated with a sonogram scan. In order to increase the chance of implantation, the endometrium should measure between 7 and 12mm and it should have a tri-layer pattern. Additionally, a blood test is done to verify if there is hyperstimulation. In case where there is, the embryo transfer will not be made during that cycle, as the endometrium will have been damaged.
Even if all the conditions are met, it is possible that implantation does not take place. Additional examinations may be required after a negative result to study the sperm (with FISH and DNA fragmentation tests), endometrial receptivity (ERA test) or the endometrial cavity (via Hysteroscopy).
Implantation depends on a number of factors and every step of the process is decisive in determining the success of the treatment.
For more information, please visit our IVF protocol page