Monitoring in IVF cycles - details

MONITORING IN VITRO FERTILIZATION (IVF) CYCLES

E. Tawfik, A. Mastrorilli and A. Campana
Infertility and Gynecologic Endocrinology Clinic,
Department of Obstetrics and Gynecology,
University Cantonal Hospital, 1211 Geneva 14, Switzerland

The term " monitoring " means " close continuous observation ", so when we refer to monitoring an in vitro fertilization and embryo transfer (IVF-ET) cycle we mean close observation not only of a patient’s initial parameters and her own ovarian response to ovulation induction, but also events after completion of the therapy.

Why monitor the patient? Monitoring serves two purposes. On the one hand, it helps the physician to choose the most suitable protocol, or to modify the dose and/or the approach for the protocol being applied in an attempt to obtain the best possible outcome and avoid complications of therapy or of the procedure as a whole. On the other hand, monitoring our patients adds to the common pool of information which increases our knowledge and understanding of human reproduction.

In our opinion, monitoring IVF patients begins with the initial infertility work-up, and continues until after delivery. This chapter is concerned, however, with the time period of an IVF cycle which starts just before induction therapy and ends either by the establishment of a biochemical pregnancy, or failure of implantation. Before discussing different methods of monitoring, it is better to divide monitoring into three stages: before starting induction therapy, the period of induction and the period that follows completion of therapy.



Before induction therapy

During this period, one has to think about which protocol should be offered to the patient. This depends on many factors such as the patient’s endocrine profile and general health, her age and financial situation, and the physician’s previous experience.

Clomiphene citrate

Before prescribing clomiphene citrate (CC), the physician should be sure that the follicle stimulating hormone (FSH) is not abnormally elevated and that the patient is not hypoestrogenic. One should rule out disorders of the pituitary, adrenal and thyroid which require specific treatment. Liver function evaluation should precede CC therapy if history and physical examination findings suggest liver disease. Ultrasonography (US) should be done just before starting the therapy to exclude ovarian cysts.

Gonadotropin therapy

If gonadotropin therapy is chosen, it is of utmost importance to exclude ovarian incompetence because this type of treatment is very expensive and is not free of complications. Abnormally high serum levels of gonadotropins with low estrogen levels indicate ovarian failure which precludes induction of ovulation except in a few special cases. Non gynecological endocrine problems should be treated before starting the therapy. Hypogonadotropic function with galactorrhea requires evaluation for an intracranial lesion. It is important to know that hyperprolactinemia has no adverse effect on ovarian response to exogenous gonadotropin therapy (8). Ultrasonography should be done to exclude the presence of ovarian cysts and/or polycystic ovary disease (PCO) which require special care.

Gonadotropin releasing hormone analogue (GnRHa) combined with exogenous gonadotropin therapy

This approach is especially effective for women who either show no response to exogenous gonadotropins, or who develop premature spontaneous luteinizing hormone (LH) and progesterone rise. Indeed the major effect appears to be the prevention of premature luteinization which is a major reason for decreased success with other therapies. Patients with significant estrogen and gonadotropin levels, especially anovulatory women with PCO do not respond well to gonadotropins but the response can improve after GnRHa desensitization. Some protocols call for GnRHa use during the luteal phase of the preceding IVF cycle, others advocate its use during the follicular phase concomitantly with human menopausal gonadotropin (hMG) and/or pure FSH. At present there is no agreement as to which protocol is best, and the information available is rather conflicting.

If it is decided to prescribe the long term GnRHa protocol, the patient should be monitored for the criteria of pituitary and ovarian suppression. Complete suppression is verified by the onset of menstruation associated with a serum LH <2>10 mm in diameter. If all these criteria are not met on day 12, GnRHa should be continued and the patient assessed at weekly intervals until suppression is complete, then induction can be started.

Monitoring ovarian response to induction therapy

Monitoring ovarian response to induction therapy depends mainly on the biophysical parameters of follicular growth, and hormonal parameters, principally E2 levels.

Monitoring follicular growth

Sonography can depict developing follicles, beginning at the time they measure between 3 and 5 mm. As follicles spontaneously reach maturity in the natural cycle their inner dimensions range from 17 to 25 mm (9). Within the same individual however, the size of a mature follicle is relatively constant. Intrafollicular echoes may be observed within mature follicles probably arising from clusters of granulosa cells that shear off the wall near the time of ovulation. After ovulation, the follicular wall becomes irregular. The fresh corpus luteum usually appears as an echogenic structure with a small hypoechoic center. Patients undergoing ovulation induction are usually examined every other day beginning at day 10, but those undergoing IVF–ET are examined earlier, usually starting between day 5 and 8 of their cycles, and daily thereafter.

In CC-treated cycles, each follicle seems to develop at an individual rate, and at times may be accelerated or slowed down. Therefore the largest follicle on a given day may not be the same one that is the largest two days later, and it may not even be the one that is most mature. Furthermore, correlation of E2 and follicle size is poor and the maximum preovulatory diameter can range from 19 to 24 mm. However, the largest diameter in these cases estimated by Fossum et al. (12) ranged between 22 and 31 mm.

In hMG-treated patients, there seem to be two distinct patterns of follicular development (35). In amenorrheic women with dormant ovaries, a small number of large follicles develops. The growth rate and E2 production are linear, correlate well and are of equal predictive value. A high pregnancy rate is achieved in this group. In contrast, stimulation of patients with estrogenic activity requires less hMG and usually results in the rapid recruitment of many follicles with different growth rates and E2 secretory capacity. The rate at which E2 increases is exponential, increasing the risk of hyperstimulation. The growth rate and functional maturity are asynchronous. In this group of women, both E2 and sonographic follicular monitoring are essential.

The biophysical indicators that correlate best with the day of LH surge (12) have been found to be the follicular volume in spontaneous cycles (range: 3.4-5.6 ml), the cross-sectional area in GnRH stimulated cycles (range 1074-1382 mm2) and the largest diameter in CC-treated cycles (range: 22-31 mm). Because no significant difference was seen in the correlation among the various biophysical variables and the mid cycle LH peak however, it could be concluded that in women ovulating spontaneously, or in those induced to ovulate with CC or GnRH, any available biophysical index will have the same predictive value. In contrast, correlation analysis in cycles treated with hMG indicates that both the follicular diameter and E2 are required for optimal timing of human chorionic gonadotropin (hCG) administration.

Sonographic delineation of follicle size is crucial because hCG is best administered once follicles reach 15 to 18 mm in size even in non-IVF cycles when ovulation is allowed to occur, as the LH surge is less frequent when hMG is used for stimulation. For IVF, follicles are typically aspirated when they reach 15 to 18 mm in average diameter and when the E2 level is approximately 400 pg/ml per large follicle (20). Another sonographic sign of mature follicles is the presence of low level intrafollicular echoes, as mentioned earlier. When follicles >15 mm are aspirated, oocytes are at all stages of maturity (23). Therefore one can rely on follicular diameters alone if the patient’s previous cycles and her E2 response are known.

There is no difference in E2 production between follicles measuring 14 mm and those that are smaller, nor between follicles measuring 17 mm and those which are larger (32). The authors devised an equation to determine expected serum E2 levels depending on number and size of follicles in both ovaries. Thus the serum E2 level on the day of hCG injection is:

E2 = 291 pg/ml + 180 (x) + 64 (y) + 18.7 (z)

where x, y and z represent follicles measuring >17 mm, 15 to 16 mm and <14>9 mm thick) and group B (<9>300 pg/ml by day 8 of stimulation. Fast responders had their E2 levels >300 pg/ml by day 5 of stimulation. However because E2 levels can be augmented to comparable levels by increasing the dose of gonadotropins, a correlation between E2 levels and gonadotropin dose is needed. Ibrahim and co-workers (16) defined poor response in desensitization protocols as the need for 4 or more ampoules of hMG/day to induce ovulation.

The dose of gonadotropin should not be changed as long as serial E2 levels rise between 50 and 100% every other day (32). Dirnfeld et al. (6), showed that very slow or very rapid estrogen growth rates (EGRs), calculated from the 4 days preceding oocyte aspiration in CC/hMG stimulated cycles, were associated with a reduced pregnancy rate. EGRs of 0.31 to 0.41 were associated with optimal pregnancy rates. EGR is calculated by the formula:

EGR = e-B -1

where B is the slope of the least square line corresponding to the semilogarithmic plot of E2 values versus time and e = 2.718.

Using GnRHa and gonadotropin in a desensitization protocol, the ovarian response was evaluated in terms of E2 levels on the day of hCG injection, and 36 hours later at egg retrieval (23). Low responders, medium responders and high responders were those with E2 levels of <800>1500 pg/ml respectively on the day of hCG injection or <400>1000 pg/ml respectively at egg retrieval. There were no differences between the three groups in respect to development of mature oocytes and rapidly cleaving embryos. The pregnancy rate in the low responding group, however, was significantly lower than in the other two groups, despite replacement of an equivalent number of oocytes and cleaving embryos. Thus it seems that the receptivity of the endometrium depends at least partially on adequate E2 levels. It also seems that E2 levels do not directly correlate with oocyte maturity and embryonic growth.

An upper limit of estradiol of 3800 pg/ml for anovulatory women (with polycystic ovaries) and 2400 for women with hypothalamic amenorrhea produces a risk of severe hyperstimulation of 5% in pregnant cycles and 1% in non conceptional cycles (14).

Paltieli and colleagues (28) found that in hMG cycles in which ovulation was triggered by using hCG injections, at least 80% of pregnancies were achieved when the E2 rise (active phase) was 6±1 days, whereas only 15% of pregnancies were achieved when the active phase was >7 days. They attributed the high incidence of early abortion, when the active phase was >7 days, to be an expression of oocyte overexposure to hMG prior to hCG injection. Such overexposure may result in postmature oocytes and end in early abortion. The same group of investigators noted also that in good outcome cycles, E2 continued to rise until hCG was administered, but in nonpregnant cycles, E2 plateaued on the day before hCG administration, which suggests that luteinization or atresia of the more advanced follicles had commenced spontaneously.

Monitoring special situations

CC/hMG protocols

Although adequate follicular development occurs with CC and hMG combination regimen, it is thought that one problem with that regimen is premature luteinization (13). In general, it is believed that the rise in serum progesterone occurs 12 hours before or on the day of the onset of a spontaneous LH surge in a natural cycle, or in a controlled ovarian hyperstimulation for IVF-ET program (36). Fleming and Coutts (10) defined the criteria for premature luteinization to be: serum progesterone >1.5 ng/ml associated with a rise in serum LH concentration before maturation of the developing follicles, together with a decline or plateauing of the serum E2 concentration despite continued hMG administration. However, there were reports that a significant rise in serum progesterone occurs in advance of the onset of the LH surge in regimens using a combination of CC and hMG (30).

In 1992, Mio and colleagues (24) defined " subtle progesterone rise " as a fluctuation in the serum progesterone concentration of between 1 and 2 ng/ml from day 7 of the cycle until 24 hours before the hCG administration, or the onset of the LH surge. This is not coupled with a significant increase in the serum LH concentration, defined as an increase of <100%>17-18 mm in diameter. Patients with poor follicular development or with only one developing follicle are not given hCG. It is inadvisable to give hCG to patients in whom the serum estradiol level is seen to increase rapidly (i.e. doubling in 24 hours) in order to minimize the risk of the OHSS.

Just prior to hCG injection, a serum LH can be drawn and compared to values earlier in the cycle. This helps to identify women who have initiated a premature LH surge (LH value 2.5 times baseline). However, without frequent sampling of LH (every 3 hours), the onset of the surge cannot be identified with precision (33). LH sampling is not required in patients who are treated with GnRHa. If a spontaneous LH surge occurs in a stimulated cycle, some centres cancel the treatment cycle, whereas others give hCG if there is a satisfactory estradiol response and adequate follicular growth has taken place (37). In these cases, it is necessary to adjust the timing of oocyte recovery.

As a general rule, hyperstimulation is associated with the presence of many follicles. It is advisable that hCG not be administered if there are more than 3-4 follicles of 14 mm or more in diameter (33). Mild hyperstimulation has been associated with an increased number of intermediate size follicles and severe hyperstimulation with an increase in small follicles (2). A large number (11 or more) of small follicles should also preclude hCG administration.

Check and colleagues (4) used hCG to trigger ovulation in their patients in whom ovulation was induced by hMG. The timing of injection of hCG was influenced by the serum progesterone level as follows: if the serum progesterone was >1.8 ng/ml, then 10,000 units of hCG would be given as long as there was at least one dominant follicle with serum estradiol >200 pg/ml, even if multiple follicles were present and the serum estradiol was <200>25 mIU/ml is diagnostic and is confirmed by a rising titre 3 days later. When pregnancy is diagnosed, it may be necessary to support it by exogenous hCG administration until 12 weeks gestation. The diagnosis of a clinical pregnancy is made when one or more gestational sacs can be identified by ultrasound image 4 to 6 weeks after oocyte retrieval. Embryonic viability is diagnosed when the heart beats can be detected on the screen.

This is not the whole story. Pregnant patients still need close follow-up and special care in relation to an expensive precious pregnancy until after labour and delivery.

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