Implantation dysfunction is unfortunately often overlooked as an important cause of IVF failure. In the pursuit of optimizing outcome with IVF, the clinician has a profound responsibility to meticulously assess and address this important issue if IVF success is to be optimized. This is especially relevant in cases of “unexplained IVF failure, Recurrent Pregnancy Loss (RPL) and in women suspected of having underlying anatomical and immunologic factors. Doing so will not only maximize the chance of a viable pregnancy but enhancing placentation, will at the same time promote the noble objective of optimizing the quality of life after birth.”
IVF success rates have been improving over the last decade. The average live birth rate per embryo transfer in the U.S.A for women under 40y using their own eggs , is currently better than 1:3 women. However, there is still a wide variation from program to program for IVF live birth rates, ranging from 20% to near 50%. Based upon these statistics, the majority of women undergoing IVF in the United States require two or more attempts to have a baby. IVF practitioners in the United States commonly attribute the wide dichotomy in IVF success rates to variability in expertise of the various embryology laboratories. This is far from accurate. In fact, other factors such as wide variations in patient selection and the failure to develop individualized protocols for ovarian stimulation or to address those infective, anatomical and immunologic factors that influence embryo implantation are at least equally important.
About 80% of IVF failures are due to “embryo incompetency” that is largely due to an irregular quota of chromosomes (aneuploidy) which is usually related to advancing age of the woman and is further influenced by other factors such as the protocol selected for ovarian stimulation, diminished ovarian reserve (DOR) and severe male factor infertility. However in about 20% of dysfunctional cases embryo implantation is the cause of failure.
Anatomical Endo-uterine Lesions: This blog article will focus on implantation dysfunction and IVF failure due to:
- Anatomical abnormalities in the uterine cavity (e.g. scarring, polyps and encroaching fibroid tumors)
- A thin endometrial lining
- Immunologic rejection of the embryos
Several studies performed both in the United States and abroad have confirmed that a dye X-Ray or hysterosalpingogram (HSG) will fail to identify small endouterine surface lesions in >20% of cases. This is significant because even small uterine lesions have the potential to adversely affect implantation. Hysteroscopy is the traditional method for evaluating the integrity of the uterine cavity in preparation for IVF. It also permits resection of most uterine surface lesions, such as submucous uterine fibroids (myomas), intrauterine adhesions and endometrial or placental polyps. All of these can interfere with implantation by producing a local “inflammatory- type” response similar in nature to that which is caused by an intrauterine contraceptive device. Hysterosonography (syn; HSN/ saline ultrasound examination) and hysteroscopy have all but supplanted HSG to assess the uterine cavity in preparation for IVF. HSN which is less invasive and far less expensive than is than hysteroscopy involves a small amount of a sterile saline solution is injected into the uterine cavity, whereupon a vaginal ultrasound examination is performed to assess the contour of the uterine cavity.
Endometrial Thickness: As far back as in 1989 I first reported on the finding that ultrasound assessment of the late proliferative phase endometrium following ovarian stimulation in preparation for IVF, permits better identification of those candidates who are least likely to conceive. We noted that the ideal thickness of the endometrium at the time of ovulation or egg retrieval is >9 mm and that a thickness of less than 8 mm bodes poorly for a successful outcome following IVF.
Then in 1993, I demonstrated that sildenafil (Viagra) introduced into the vagina prior to hCG administration can improve endometrial growth in many women with poor endometrial development. Viagra’s mechanism of action is improvement in uterine blood flow with improved estrogen delivery…thereby enhancing endometrial development.
Immunologic factors: These also play a role in IVF failure. Some women develop antibodies to components of their own cells. This “autoimmune” process involves the production of antiphospholipid, antithyroid, and/or anti-ovarian antibodies – all of which may be associated with activation of Natural Killer (NK) cells in the uterine lining. Activated NK cells (NKa) release certain cytokines (TH-I) that if present in excess, often damage the trophoblast (the embryo’s root system) resulting in immunologic implantation dysfunction (IID). This can manifest as “infertility” or as early miscarriages). In other cases (though less common), the problem is due to “alloimmune” dysfunction. Here the genetic contribution by the male partner renders the embryo “too similar” to the mother. This in turn activates NK cells leading to implantation dysfunction. These IID’s are treated using combinations of medications such as heparin, Clexane, Lovenox, corticosteroids and intralipid (IL).