Essentially, it is considered recurrent implantation failure (RIF), whereas in any other case where healthy embryos do not exist, the diagnosis is different (e.g. low follicle sufficiency).
The reasons why a couple may be dealing with repeated failures could be due either to embryo abnormalities or to uterine problems.
Embryo abnormalities, especially chromosomal ones, are very common both in natural cycles (natural conception) and in IVF cycles. Indeed, they are the most common cause of miscarriages and IVF failures. They are mainly due to egg quality, which is related to the woman’s age and occasionally to the sperm’s quality (DNA fragmentation rate). In general, the couple’s lifestyle, their diet, exercise, stress levels and habits such as smoking, are important factors.
Microscopic screening in the laboratory cannot reveal abnormalities in the genetic material, because these do not manifest in the early embryonic stage. The only way to diagnose chromosomal anomalies is Preimplantation Genetic Screening (PGS); however, this is an invasive method that is only recommended by a specialised physician.
There are indirect ways to assess egg quality, or egg capacity to develop, in order to select only the adept or most adept for embryo transfer. These methods are based on the embryos’ morphological characteristics during development or on the assessment of biochemical markers produced by the eggs, such as the sHLA-g protein. Even embryo transfer on the 5th day after fertilisation is a natural way of selecting the embryos with the greatest development potential. This reduces the probability of failure and, of course, increases the chances of a healthy pregnancy.
Uterine abnormalities linked to repeated IVF failures are divided into anatomical malformations, congenital (uterine septum) or acquired (such as fibromas, endometrial polyps, and intrauterine adhesions due to infection).
A very important success factor for implantation is the achievement of a healthy endometrium with adequate thickness (over 7 mm) and synchronised with the embryo (–window of implantation). –Adhesions due to previous surgical interventions in the uterus (such as curettage) hinder the development of endometrial thickness.
The diagnosis of all of the above conditions is possible with a series of suitable tests, such as ultrasound, hysteroscopy, diagnostic laparoscopy, salpingography and MRI.