What is implantation failure?
There is no single universally accepted definition for Recurrent Implantation Failure (RIF). However, the most commonly proposed definitions is failure to achieve a clinical pregnancy after the transfer of at least 2-3 good-quality embryos in multiple transfer cycles. Some definitions are more specific and include maternal age and embryo chromosomal status.
Chromosomal abnormalities in the embryo are a common invisible cause of implantation failure. It has been estimated that approximately 72% of implantation failure cases are caused by chromosomal abnormalities in the embryo. The tool that allows us to evaluate the chromosomal number in the embryo is Preimplantation Genetic Testing (PGT). This diagnostic method provides information about the chromosomal status of each conceived embryo before transferring it to the maternal uterus. This ensures that embryos with a normal number of chromosomes can be selected for transfer. The PGT technique is the result of combining In Vitro Fertilisation and genetic analysis.
The sperm must be able to reach the released oocyte (egg) through the uterus and the fallopian tubes. A few days after the fertilisation, the embryo reaches the uterus and implants in its inner membrane layer, called the endometrium. Suitable conditions of the endometrium are required for the placenta and foetus to develop.
A blocked or damaged fallopian tube can prevent sperm from reaching the egg or the fertilised egg (zygote) from passing into the uterus for implantation.
Anomalies in the uterus or pelvis can prevent the fertilized egg from adhering to the uterine lining and block the tubes. If tubal damage is confirmed, the necessary treatment is In Vitro Fertilisation, IVF.
The initial assessment of the uterus is done with a vaginal ultrasound. This allows careful observation of the uterine structures, the endometrial cavity and the ovaries. Anomalies such as fibroids, uterine polyps and ovarian cysts can be diagnosed, which in some cases may require surgery. Some patients will need a more in-depth evaluation of the endometrium. A history of miscarriages or pelvic infections or abnormalities in the ultrasound evaluation may necessitate hysteroscopy or an endometrial biopsy to appropriately assess the possible underlying causes of infertility, propose suitable treatment options accordingly, and estimate the likelihood of achieving pregnancy.
The hysteroscopy may be carried out at the doctor’s office, but more commonly at a separate dedicated procedure room. A thin cannula connected to a screen is inserted through the cervix to visualise the endometrial cavity. Samples (biopsies) may also be taken for detailed evaluation of the endometrium (to rule out infections, immunological imbalances and ensure appropriate hormonal milieu).
An endometrial biopsy to assess the presence of chronic endometritis, endometriosis activity, or various immunological abnormalities can often be performed without hysteroscopy during a routine gynecological examination. Endometritis is a chronic infection that amy not cause symptoms in the patient but can prevent embryo implantation. In these cases, antibiotic treatment is indicated.
To study the vascularisation of the endometrium, a vaginal Doppler ultrasound is performed, which allows us to rule out alterations in blood flow.
To study the permeability of the fallopian tubes, a hysterosonosalpingography is performed. This is carried out during a fertility specialist appointment in the first half of the menstrual cycle, before ovulation. It involves injecting a saline infusion or contrast medium through the cervix that fills the uterine cavity and the tubes and exits into the abdomen. The ultrasound scan is performed simultaneously with the saline infusion.
If the result of the test is normal, the tubes are considered to be permeable, although it does not assure us that they perfectly fulfil all their functions of transport of gametes and embryos.
If the result is pathological, a tubal factor can be diagnosed, for example, if the passage of the contrast is obstructed or hydrosalpinx (pathological dilation of the tubes) is observed. In rare cases, the result is inconclusive and a diagnostic laparoscopy is advised to better assess the tubal function.
The tubes can be affected by pelvic infections (currently the most common causative pathogen is Chlamydia), endometriosis or the condition may be secondary to gynaecological or abdominal surgery.
