Investigation and Clinical Approach of Recurrent Implantation Failure

Recurrent implantation failure (RIF) derives from the practice of IVF. The ability to identify implantation failure after the transfer of embryos raised the possibility that there exists a patho-physiological state leading to repeated implantation failure. RIF can be defined as the repeated lack of implantation after the transfer of embryos. Prior to IVF, treatment resulted either in a pregnancy or not. IVF added the ability to further compartmentalize the treatment process so that it became possible to know when an embryo was transferred and if an implantation occurred. Hence RIF became a possible clinically identifiable phenomenon. The relevance of defining such a problem lies in the ability to diagnose patho-physiological conditions, which might be amenable to treatment and thus increase the implantation rate thereby increasing a couple’s chance of conception.

Many practical procedural problems exist when trying to define implantation failure. One limitation when defining implantation and implantation failure is that at present, implantation can only be determined by a rising quantitative hCG level which occurs a number of days after implantation has actually occurred or failed. There remains a time-frame which cannot be further compartmentalized and thus limits the ability to precisely define the cause of implantation failure. Thus, for practical purposes, implantation is defined as a rise in the quantitative hGC level determined at some point after embryo transfer. The most accurate way to determine this would be to do daily serum HCG levels starting after embryo transfer. But again practicality dictates that the first level is drawn at some point after embryo transfer and for many programs this is usually 10–14 days after hCG is given.

The timing of when the first hCG determination is performed will affect the implantation rate. The earlier the first hCG determination is done, the lower the failed implantation rate will be since some pregnancy losses will occur prior to the hCG determination for those programs measuring it later in the cycle. Any definition of RIF requires a standardization of the time from embryo transfer to the time used to determine a positive hCG level. The definition also needs to establish what will be considered a pregnancy when using hCG. For example, will any value above the threshold value be considered evidence of implantation or will there need to be rising hCG levels? Finally, the day of embryo transfer needs to be established. For example, suppose there was a preventable cause of failed implantation that occurred at the morula stage. Programs transferring day three embryos would have a higher failed implantation rate than those programs transferring blastocyst embryos.

The accuracy of a clinical definition is to a large extent determined by the simplicity or, conversely the complexity, of the problem. A physiologic process that has a single factor is easy to define in its entirety. A pathological process that alters the physiology of the process in question may be caused by a single factor and, if measurable, the definition of the disease process is simple and accurate. The thesis of this manuscript has two prongs. First, implantation is extremely complex and highly redundant. Continuation of the species is evolutionarily a high priority. Therefore, the evolutionary process has preserved the ability to implant through accruing a number of individual processes, many of which are, in and of themselves, not necessary, but collectively contribute to a maximum chance for implantation. Second, because of the complexity and redundancy of implantation, assigning etiologies for implantation failure and RIF will be difficult.

There are some processes involved in implantation which are simple and absolutely required for implantation to occur. But there are many processes which are not necessary but contribute to implantation. Therefore, the problem with implantation failure as well as RIF is not in defining the problem, which is self-evident, but in assigning causality to the phenomenon. Some causes of IF and RIF will be a single factor. Their identification and their contribution will be easier to discern. However, implantation failure and RIF may be a result of a threshold phenomenon whereby there are a multitude of factors required for maximum implantation efficiency. A failure of any one of these factors might, or might not, reduce the overall implantation rate. But to reach a state whereby implantation failures, or implantation fails repeatedly, might require errors in a number of factors and might not be the same factors for each case of IF or RIF. The identification of this problem becomes complex and very difficult to approach experimentally.

Any deviation from or interruption of the normal structure or function of any part, organ, or system, or combination thereof, of the body that is manifested by a characteristic set of symptoms or signs, and whose etiology, pathology, and prognosis maybe known or unknown. Implantation failure and especially to recurrent implantation failure demonstrates just how difficult it becomes to define a disease. There are two ways of approaching a definition for a normal implantation rate: evaluate spontaneous pregnancy rates in fertile couples, or evaluate implantation rates when using donor oocytes. There are many factors intervening when couples have intercourse which could result in a less than perfect system so that more than 50% of the cycles do not result in a pregnancy. Therefore, using the natural pregnancy rate in maximally fertile women does not provide the best definition of a normal implantation rate.

IVF provides a more definable system since it involves oocyte, sperm and, endometrium. For this more defined system, the relevant statistic is not normal implantation rate but rather, the maximum implantation rate. Any deviation from this maximum implantation rate would represent a compromise that is, by definition, a disease. Identifying the maximum implantation rate requires evaluating implantation rates obtained through the use of normal oocytes, sperm, and endometrium when the IVF procedure is done by the technically most adept IVF units. This condition is frequently met for women using donor oocytes for age-related ovarian failure. The implantation rate for the double embryo transfer patients was equally high at 56%. It would appear that the maximum implantation rate for IVF is between 40% and 60%. For IVF programs with substantially lower implantation rates, the problem may be technical related to either the clinical or laboratory components of the program. Until a program’s implantation rates meet industry standards, evaluating the patient for problems with implantation failure will be premature.

Defining the term “recurrent” is very challenging, analogous to defining infertility or recurrent pregnancy loss. A problem when using pregnancy rates based upon number of transfer cycles relates to the variability of the number of embryos transferred on any given cycle, the quality of the embryos transferred, and the day of embryo transfer. Defining recurrent implantation failure as three unsuccessful IVF attempts actually defines RIF in terms of failed IVF cycles and does not address the issue of implantation rates. Some patients may have a large number of poor quality embryos transferred for a given IVF cycle; whereas, others may have only one or two embryos transferred. Thus, defining RIF in terms of pregnancy rate does not allow an evaluation of the implantation rates. Also, the day of transfer greatly impacts the pregnancy rate since blastocyst embryos have a higher implantation rate than day three embryos.

Therefore, time to pregnancy should be shorter for cycles with blastocyst transfers and especially if many blastocysts are transferred on a given cycle. For example, transferring three blastocyst embryos should result in a pregnancy sooner than transferring only a single blastocyst embryo. The definition of RIF would be fewer transfer cycles for multiple optimal embryos transferred per cycle than for either poorer quality embryos, high quality embryos transferred on day three, or fewer blastocyst embryos per cycle. Age also has an impact on the pregnancy rate and is a known factor for implantation failure. Thus, defining recurrent differs depending upon the age of the population studied. Finally, the choice of the number “three” deserves some attention. For three to be the operational number of IVF cycles, there needs to be some correlation with that number and the incidence of implantation failure. For example, the cycle fecundity needs to decline after three cycles of IVF if RIF is defined by the number of cycles for transfer. Where there is no implantation failure, the cycle fecundity rate remains constant. The cycle fecundity rates of 36.2% for each of the first four cycles of donor oocyte embryo transfers.

However, cumulative pregnancy rates for IVF have demonstrated a decline in cycle fecundity with successive failed IVF cycles. A clinical pregnancy rate of 19.0% for the first IVF cycle, 17.4 for the second, 11.8 for the third, 10.8 for the fourth, and less than 6% for the next three successive cycles of IVF. Defining RIF after three cycles of IVF with this data is problematic given the fact that is seems the number should be either two or four cycles of IVF. Furthermore, notes an even more dramatic decline in pregnancy rates with successive IVF cycles where the embryos transferred were blastocyst embryos. The cycle fecundity rates were 36% for the first transfer, 19% for the second, and 9% for the third. Given this data, RIF may need to be defined as failed two or even one cycle of transfers with blastocyst embryos.

A second method of defining RIF uses the number of embryos transferred. All consecutive pregnancies from a large IVF program were analyzed to determine the total number of embryos that had been transferred to achieve each pregnancy. The number to achieve 80% of the pregnancies was 8 and for 95% of the pregnancies it was 12. Arbitrarily defining normal at the 95 percentile, RIF was defined as having failed to achieve a viable pregnancy if more than 12 embryos had been transferred. The patients participating in this study were all infertility patients and, thus, the pregnancy rates were not maximal as they might have been had donor oocyte recipient patients been used. The pregnancy rates and implantation rates were below what they are today, and these pregnancies were achieved using day three transfers, not blastocyst transfers. Therefore, the number used to define RIF would be lower today and depend upon whether day three or blastocyst transfers were being considered.

Any definition of RIF will be found wanting given the complexity and redundancy of the implantation process. However, a working definition of RIF can be based upon the number of embryos transferred. The definition will depend upon the stage of embryo development. The actual number will vary by center and can best be calculated by using pregnancies delivered in patients using donor oocytes. The definition of RIF used in our program requires the transfer of =8, 8-cell stage embryos or =5 blastocyst embryos. Evidence of implantation is accepted when there is a rise in hCG for hCG measurements made 12 and 14 days after the hCG injection that is given to trigger the time of retrieval.

Assessment of low and high beta HCG: Unveiling the Secrecy

If you visit any forum or infertility group discussion; you are sure to find questions and worried about HCG levels. The posted inquiries run the gamut from “is my beta too low,” to “do you think my number is high enough to indicate twins?” After my initial beta I was one of the many searching out information on HCG and whether or not my number was good or bad. Looking at other people’s beta levels and doubling times really can help ease some of the worry that goes along with just not knowing what it all means. On that site they only put betas in the chart once a heartbeat has been detected so it can be reassuring to read that there was a successful pregnancy that began with a beta level of 3 at fifteen days past ovulation or that some of the successful pregnancies had slower than average doubling times.

The craziness surrounding beta HCG levels is kind of unique to the world of infertility. People who conceive naturally often don’t even think about their HCG levels unless something goes wrong and the doctor orders the quantitative test. Those who have been through treatment spend their two-week wait counting down the days until beta day. If you are lucky enough to get a positive beta, try counting down the days until the second beta so you can get the more important information of your doubling time or even better (and much more difficult) see if you can hold out and not freak out until your ultrasound at 5-6 weeks. The first ultrasound will tell the tale of your pregnancy much more accurately and if you can do it; you will save yourself much worry and concern.

The hormone human chorionic gonadotropin (better known as HCG) is produced during pregnancy. It is made by cells that form the placenta, which nourishes the egg after it has been fertilized and becomes attached to the uterine wall. Levels can first be detected by a blood test about 11 days after conception and about 12 - 14 days after conception by a urine test. In general the HCG levels will double every 72 hours. The level will reach its peak in the first 8 - 11 weeks of pregnancy and then will decline and level off for the remainder of the pregnancy.

“An HCG level of less than 5mIU/ml is considered negative for pregnancy, and anything above 25mIU/ml is considered positive for pregnancy.”

Each and every patient or couple undergoing IVF, makes a huge emotional, physical and financial investment. The fact that receiving the result of the beta HCG (human chorionic gonadotropin) pregnancy test represents the first decisive hurdle that must be confronted, makes this a very big deal!! The few days after the embryo transfer, waiting for this first outcome report from your fertility clinic is usually anxiety ridden and highly stressful. It is thus imperative that the Fertility Specialist and his/her staff deal delicately with the transfer of this critical information. Dropping the ball at this time would be unconscionable. The physician and staff must make themselves accessible to the patient/couple and communicate the results promptly, professionally and with sensitivity.

A single HCG reading is not enough information for most diagnoses. When there is a question regarding the health of the pregnancy, multiple testing of HCG done a couple of days apart give a more accurate assessment of the situation.

The HCG levels should not be used to date a pregnancy since these numbers can vary so widely.

HCG levels in weeks from LMP (gestational age)*:

      1.       3 weeks                               LMP:      5 - 50 mIU/ml

      2.       4 weeks                               LMP:      5 - 426 mIU/ml

      3.       5 weeks                               LMP:      18 - 7,340 mIU/ml

      4.       6 weeks                               LMP:      1,080 - 56,500 mIU/ml

      5.       7 - 8 weeks                         LMP:      7, 650 - 229,000 mIU/ml

      6.       9 - 12 weeks                       LMP:      25,700 - 288,000 mIU/ml

      7.       13 - 16 weeks                     LMP:      13,300 - 254,000 mIU/ml

      8.       17 - 24 weeks                     LMP:      4,060 - 165,400 mIU/ml

      9.       25 - 40 weeks                     LMP:      3,640 - 117,000 mIU/ml

Non-pregnant females: <5.0 mIU/ml and Postmenopausal females: <9.5 mIU/ml

* These numbers are just a Guideline- every woman’s level of HCG can rise differently. It is not necessarily the level that matters but rather the change in the level.

What can a Low HCG level mean?

A low HCG level can mean any number of things and should be rechecked within 48-72 hours to see how the level is changing. A low HCG level could indicate:

  v  Miscalculation of pregnancy dating

  v  Possible miscarriage or blighted ovum

  v  Ectopic pregnancy

What can a high HCG level mean?

A high level of HCG can also mean a number of things and should be rechecked within 48-72 hours to evaluate changes in the level. A high HCG level can indicate:

  v  Miscalculation of pregnancy dating

  v  Molar pregnancy

  v  Multiple pregnancy

  v  Should my HCG level be checked routinely?

While it can be interesting to see what other people’s beta levels are it is important to remember that the number itself is not the most telling or reliable. HCG is the hormone made by pregnancy that is detected to indicate that a woman is pregnant. In general HCG levels will double every 2-3 days in early pregnancy. 85% of normal pregnancies will double every 72 hours and doubling is often more important that the actual HCG number. There is definitely a large variation in “normal” HCG numbers, and it is advisable to resist the urge to compare to others. That being said, I know from personal experience that it is really hard not to seek out information about the levels and even more difficult to just wait patiently for the ultrasound as recommended.

At least two quantitative beta HCG blood tests are done (2-4 days apart). The reporting of “beta” pregnancy test results is best deferred until after the 2nd blood test results are in. This is because a successful IVF outcome will (in younger women) result at best in 50-55% of cycles (with the notable exceptions of IVF using an egg donor and the transfer of genetically [CGH] tested “competent” embryos).  Thus, it is important to counsel patients in advance of them undergoing beta HCG testing to have rational expectations. It is equally important to inform patients exactly how, when, and from whom they will receive the report of their beta HCG results, because they are about as likely to get “bad news” as they are likely to hear “good news”. Thus I usually advise my patients to “prepare for the worst while hoping for the best” and that in the event of a “negative” result they will have prompt access to me (or a designee) for counseling.

As soon as an embryo begins to implant and its root system begins to invade the uterine lining.  it starts to release the “pregnancy hormone” human chorionic gonadotropin (HCG) into the recipient’s blood stream. About 12 days after egg retrieval, 9 days after a day-3 embryo transfer and 7 days after a blastocyst transfer, the woman should have a quantitative beta HCG blood pregnancy test performed. By that time almost all HCG injected to prepare the developing eggs for egg retrieval should have left the woman’s bloodstream. Thus the detection of >5 IU of HCG per ml of blood tested is an indication that the embryo has attempted/begun to implant. Since with third-party IVF (i.e. Ovum donation, gestational surrogacy, embryo adoption) or frozen embryo transfers, no HCG “trigger shot” is administered, the detection of any amount of HCG in the blood is regarded as significant.

Often times, an initial rise in HCG (between the 1st and 2nd test) will be slow (failure to double every 48 hours). When this happens, a 3rd and sometimes even a 4th HCG test should be done at 2-day intervals. A failure to double on the 3rd and/or 4th test is a poor prognostic sign. It usually indicates a failed or “dysfunctional” implantation but in some cases a progressively slow rising HCG level might point to a tubal (ectopic) pregnancy. Diagnosis requires additional serial blood HCG testing, ultrasound examinations and clinical follow-up to detect any symptoms or signs of an ectopic pregnancy.  

In some cases the 1st beta HCG level starts high and then drops with the 2nd test, only to re-start doubling every 2 days thereafter. This sometimes suggests that there were initially more than one embryo implanting and that one of these subsequently succumbed and one survived to continue a healthy singleton pregnancy. It is customary for the IVF clinic staff to call the patient/couple (and when applicable, notify the referring physician) with the results of the HCG pregnancy test. Often times, the IVF doctor or nurse-coordinator will work through the office of the referring physician to arrange for the all pregnancy tests to be done. If the patient/ couple prefer to make his/her/their own arrangements, the IVF program should provide them with detailed instructions as to how/when and where these tests should be done.

In the event that serial blood quantitative beta HCG pregnancy tests indicate that one or more embryos are likely to be implanting, some IVF physicians advocate daily injections of progesterone or the use of vaginal hormone suppositories for several weeks to support the implanting embryo(s). Others, including several physicians prefer to prescribe HCG injections three times a week for several weeks until the pregnancy can be defined by ultrasound. Some IVF centers do not prescribe any hormones at all, after the transfer.

Patients who undergoing frozen embryo transfer, egg donor, or surrogate cycles and who have blood HCG levels that show the appropriate 2-day doubling; will receive estradiol and progesterone injections and/or vaginally administered hormone suppositories, for 10 weeks following the diagnosis of implantation by blood pregnancy testing. A “clinical pregnancy” is defined as one where there is clear ultrasound evidence of an intrauterine gestation. Such confirmation is usually sought two to three weeks after the first “positive” beta HCG test.

A chemical pregnancy is one where in spite of the beta HCG test being positive it fails to progress to the point of ultrasound confirmation. Chemical pregnancies occur quite frequently following IVF. While they usually result from a chromosomally abnormal embryo trying to implant, they can also be due to the uterine lining (being insufficiently receptive to allow healthy embryo implantation. Clearly, to the IVF patient, the diagnosis of a “chemical pregnancy” represents a severe disappointment. However its occurrence provides clear evidence that at least one embryo reached the advanced preimplantation phase of development went on to “hatch” and attempted to implant.

The chance of miscarriage progressively decreases from the point of diagnosing a viable clinical pregnancy. From this point on, the risk of miscarriage is usually less than 15% in women under 39 years of age and less than 35% in women in their early forties.

Conveying news of a “positive” beta HCG result is easy. Everyone feels elated and vindicated; It is dealing with the unsuccessful case that offers the real challenge. In this regard, nothing is more important than establishing rational expectations from the get-go. In some cases, the patient/couple will crack under the emotional pressure and will require referral for counseling and in some cases psychiatric therapy.