Outlook Hopes and facts about mild ovarian stimulation

Transcription

1 RBMOnline - Vol 14. No Reproductive BioMedicine Online; on web 17 April 2007 Outlook Hopes and facts about mild ovarian stimulation Filippo Maria Ubaldi graduated with honours in medicine at the University of Rome in He obtained the specialization in obstetrics and gynaecology in From 1993 to the end of 1996 he worked as staff specialist at the Centre for Reproductive Medicine of the Dutch-Speaking Brussels Free University. In 1997 he was appointed the clinical director of the Centre for Reproductive Medicine of the European Hospital in Rome. Since 2000 he has been Professor of Endocrinology in Human Reproduction at the school of specialization in Obstetrics and Gynaecology in the University of Perugia, Italy. Dr Filippo Maria Ubaldi F Ubaldi 1, L Rienzi, E Baroni, S Ferrero, M Iacobelli, MG Minasi, F Sapienza, S Romano, A Colasante, K Litwicka, E Greco Centre for Reproductive Medicine, European Hospital, Via Portuense Rome, Italy 1 Correspondence: Fax: ; ubaldi.fm@tin.it Abstract Over the last two decades, easier and less expensive stimulation treatments have been largely replaced by more complex and more demanding protocols. Since the mid-nineties, long-term gonadotrophin-releasing hormone agonist stimulation protocols have been widely used. Such lengthy expensive regimens are not free from short- and long-term risks and complications. Mild stimulation protocols reduce the mean number of days of stimulation, the total amount of gonadotrophins used and the mean number of oocytes retrieved. The proportion of high quality and euploid embryos seems to be higher compared with conventional stimulation protocols and the pregnancy rate per embryo transfer is comparable. Moreover, the reduced costs, the better tolerability for patients and the less time needed to complete an IVF cycle make mild approaches clinically and cost-effective over a given period of time. However, further prospective randomized studies are needed to compare cumulative pregnancy rates between the two protocols. Natural cycle IVF, with minimal stimulation, has been recently proposed as an alternative to conventional stimulation protocols in normo- and poor responder patients. Although acceptable results have been reported, further large prospective randomized studies are needed to better evaluate the efficacy of these minimal regimens compared with conventional stimulation approaches. Keywords: ICSI, IVF, mild ovarian stimulation, minimal ovarian stimulation, natural IVF cycle Introduction Although the first successful pregnancy after IVF and embryo transfer was performed in the natural unstimulated cycle of an infertile woman with a tubal factor (Steptoe and Edwards, 1978), it was soon observed that pregnancy rates per IVF attempt increase when more than one embryo is transferred into the uterine cavity (Laufer et al., 1983). Subsequently, natural cycle IVF was replaced by stimulated cycles, allowing significant clinical outcome improvement. Over the last 25 years, different stimulation protocols have been proposed. More complex and more demanding protocols have gradually replaced easier stimulation regimens, such as clomiphene citrate alone or in combination with human menopausal gonadotrophin and urinary FSH. At the beginning of the nineties, short-term treatments with gonadotrophinreleasing hormone (GnRH) agonists and gonadotrophins were abandoned in favour of long-term GnRH agonist stimulation protocols. These lengthy expensive protocols, which still are the most widely used treatments for ovarian stimulation, allow easier management of the activity of the IVF centres, lower cancellation rates, and raise the number of pre-ovulatory follicles, the oocytes retrieved and the good quality embryos for transfer, thus leading to better pregnancy rates (Hughes et al., 1992). However, these regimens are not free from complications and costs for the patients. Several negative consequences and risks are sometimes reported, the most important one being, without any doubt, ovarian hyperstimulation syndrome (OHSS), a well-known complication that can become severe (Beerendonk et al., 1998). Every year, thousands of patients are hospitalized because of severe OHSS, which has high cost implications for the patients and society. Moreover, social aspects are also a concern: the complexity of these treatments entails weeks of daily injections, multiple blood samples and frequent ovarian ultrasound scans that can impact on women s lives and careers Published by Reproductive Healthcare Ltd, Duck End Farm, Dry Drayton, Cambridge CB3 8DB, UK

2 676 These side effects associated with the treatment itself (Olivius et al., 2004), together with the high costs and the relatively poor prognosis of the technique (Goverde et al., 2000), are responsible for a 25% drop-out rate after an unsuccessful IVF attempt (Osmanagaoglu et al., 1999). This high drop-out rate is partially due to the fact that 50% of patients who initiate IVF will not conceive (Stolwijk et al., 2000). It could be possible that reducing the stress, discomfort, side effects and complications that can be associated with these standard stimulation protocols, by using more friendly treatments, the drop-outs from IVF may decrease and the IVF attempts per patients and, subsequently, the birth rates per started treatment might increase (Heijnen et al., 2004). Besides patients burden, ethical dilemmas for storage and disposal of extra embryos and specific restrictive national IVF legislations have to be considered when choosing an ovarian stimulation protocol. In Italy, for instance, the new IVF legislation (Law 40/2004) (Benagiano and Gianaroli, 2004) limits very much the advantages of obtaining many oocytes from standard stimulation protocols. The legislation set a limit of three on the generation of embryos by IVF or intracytoplasmic sperm injection (ICSI), all of which should be transferred in the initial treatment cycle. The obligation to transfer all the embryos obtained after the insemination of a maximum of three oocytes and the prohibition of embryo cryopreservation raise even more doubts on the opportunity to use standard heavy stimulation protocols. The clinical introduction of GnRH antagonists in IVF (Albano et al., 2000; Olivennes et al., 2000; Fluker et al., 2001), with their immediate suppression of the pituitary function, allows the administration of low doses of gonadotrophins from midfollicular phase resulting in a more patient-friendly stimulation protocols (De Jong et al., 2000; Hohmann et al., 2003) with fewer days of stimulation, less total gonadotrophins administered and fewer oocytes retrieved. However, if these milder protocols may improve patients compliance, reducing the burden of IVF on the couple, the question that remains to be answered is whether the reduced number of oocytes obtained after mild stimulation protocols and the use of GnRH antagonists (Al- Inany et al. 2006; Griesinger et al., 2006) impair the clinical outcome. Before addressing this question, the physiology of the ovarian function is relevant to understand and proposed new treatment strategies will be reviewed. Physiology of follicular development About primordial follicles are present in the human ovary at birth and, from this moment until menopause, these follicles continuously develop into mature secondary follicles within several months (Gougeon, 1996; McGee and Hsueh, 2000). The development of early stages of follicles (from primordial to secondary class 4 follicles) is probably FSH independent whereas the final stages of follicular development (from secondary class 5 to pre-ovulatory follicles) are heavily FSH and LH dependent (Gougeon, 1986). The sudden fall of oestrogen, inhibin A and progesterone during the late luteal phase of the menstrual cycle, due to the demise of corpus luteum, is responsible for the increased frequency of pulsatile GnRH secretion, which induces rising FSH concentrations at the end of the luteal phase (Le Nestour et al., 1993). When the rise in serum FSH reaches a critical threshold level for ovarian stimulation, class 5 follicles departing from the resting pool are recruited and start a well-characterized growth trajectory (Hodgen, 1982; Gougeon and Testart, 1990). In the early follicular phase, the increased production of oestrogens, due to the FSH dependent granulosa cell aromatase activity, together with the increase of inhibin B are responsible for the falling circulating concentrations of FSH (Messinis and Templeton, 1990; Van Der Meer et al., 1994), restricting the time where FSH concentrations remain above the threshold (Baird, 1987; Brown, 1978). As a result, the dominant follicle continues its growth probably due to up-regulation by intraovarian factors that may increase sensitivity to FSH stimulation (Erickson and Danforth, 1995; Fauser and Van Heusden, 1997), whereas other non-dominant follicles of the same cohort enter atresia, due to diminished sensitivity to FSH and oestrogen biosynthesis as well as elevated intrafollicular androgen concentrations (Zeleznik and Kubik, 1986; Van Santbrink et al., 1995; Fauser and Van Heusden, 1997). On the basis of these findings, the FSH window concept has been introduced, suggesting the importance of the duration of FSH elevation above the threshold concentration rather than the height of the elevation of FSH for single dominant follicle selection (Brown, 1978; Baird, 1987; Fauser, 1994). In support of the FSH window theory is the observation that injecting a single bolus of 375 IU of FSH in the early follicular phase around the onset of menses induces an increased growth of small follicles during subsequent days without, however, affecting the dominant follicle growth (Schipper et al., 1998). In contrast, if only 75 IU of FSH is administered for 5 days from day LH + 19 until day LH + 23, extending the duration of FSH concentrations, the physiological decrease in FSH concentration is prevented and multiple dominant follicles can be observed (Schipper et al., 1998). These data confirm similar observations previously reported in primates (Zeleznik et al., 1985). Besides the duration of FSH administration, the timing of the FSH start is also an important tool for tailoring the number of growing follicles. The administration of 75 IU of FSH from cycle days 3, 5 and 7 until the day of human chorionic gonadotrophin (HCG) administration induces multiple follicular growth in the majority of normovulatory patients. However, if multiple dominant follicles can be obtained in more than 70% of patients when FSH is started on cycle days 3 or 5, this is only possible in about 35% of patients when the gonadotrophin starting date is cycle day 7 (Hohmann et al., 2001). It is possible that, in those subjects who failed the multiple follicular growth, the low daily amount of exogenous gonadotrophin was not sufficient to keep the FSH concentrations above the FSH threshold to allow more than one follicle to grow. Increasing the starting dose of FSH might increase the number of patients with multiple dominant follicles (Cédrin-Durnerin et al., 2006). This insight into the significance of the timing of initiation and duration of exogenous FSH on the dynamics of follicle development allows better understanding for the development of milder ovarian stimulation protocols. Mild ovarian stimulation protocols: clinical aspects The necessity to develop and propose milder treatment strategies for ovarian stimulation, in order to reduce the risks and the costs

3 of the standard stimulation protocols and improve physical and psychological compliance for the patients, has to be weighted against the possible negative effects that the reduced number of oocytes retrieved could have on the IVF clinical outcome. The finding that starting with a low gonadotrophin dose during the mid-follicular phase induce multiple pre-ovulatory follicles in a proportion of patients comparable to that observed when the FSH is started in the early follicular phase (Hohmann et al., 2001) suggested the proposal of stimulation protocols where the exogenous gonadotrophins are started in the midfollicular phase combined with GnRH antagonists to prevent LH rise (Bouchard and Fauser, 2000; De Jong et al., 2001; Hohmann et al., 2003). In a prospective randomized study, the clinical outcome of three stimulation regimens for IVF was compared: group A, GnRH agonist protocol; group B, early follicular phase GnRH antagonist protocol; and group C, mid-follicular phase GnRH antagonist protocol (Hohmann et al., 2003). In group A, the GnRH agonist was started in the late luteal phase of the previous cycle and, after down-regulation was achieved, ovarian stimulation was commenced with a low dose of recombinant FSH (rfsh). In groups B and C, the GnRH antagonist was initiated when the largest follicle had reached a diameter of 14 mm and the low dose of rfsh was started on cycle day 2 (group B) or on cycle day 5 (group C). In this latter group, the duration of stimulation was shorter, the total dose of rfsh used was lower but more cycles were cancelled due to low ovarian response. However, the quality of the embryos was better resulting in more embryo transfers per oocyte retrieval. The pregnancy rates per started cycle were comparable among the three groups. More interestingly, when the number of retrieved oocytes was low (four or less) in group A and B (profound stimulation), the pregnancy outcome was impaired, whereas in patients treated with the mild regimen, the lower number of oocytes retrieved was associated with a good chance of pregnancy (67% of these patients conceived). A low ovarian response after profound stimulation is a marker of reduced ovarian reserve and poor oocyte quality (Beckers et al., 2002; Nikolaou et al., 2002; Ubaldi et al., 2005). On the other hand after mild stimulation regimens, patients with a normal ovarian reserve may have a reduced number of oocytes retrieved representing a more physiological oocyte selection rather than ovarian ageing. This could make it possible to obtain better quality oocytes and embryos, as observed in the study by Hohmann et al. (2003). Recently, a combination of clomiphene citrate and gonadotrophins with or without the use of GnRH antagonists has been proposed as a mild stimulation regimen. The efficacy of clomiphene citrate in combination with gonadotrophins was compared with a long agonist protocol in four studies (Engel et al., 2002; Weigert et al., 2002; Williams et al., 2002; Hwang et al., 2003). In all the studies, a reduction of the total amount of gonadotrophin administered and of the number of oocytes retrieved was reported in the mild protocols. The pregnancy rates per fresh transfer were comparable in the two groups but the lower number of oocytes retrieved and embryos obtained with the mild regimens could impair the cumulative pregnancy rate in this group of patients. Further studies are needed to compare the clinical efficacy per started cycle between the two protocols. Similar results have been observed in the authors study centre. From January to December 2006, 43 normovulatory young patients (age 38 years) with serum basal FSH concentrations <10 mui/ml underwent a mild ovarian stimulation for IVF (unpublished). Low dose exogenous gonadotrophins were started on cycle day 5 and when the dominant follicle reached a diameter of 14 mm, GnRH antagonist was administered subcutaneously every 24 h until the day of HCG administration. Each mild stimulation cycle was matched with a long GnRH agonist stimulation protocol, where the GnRH agonist was started in the late luteal phase of the previous cycle, and after downregulation was achieved ovarian stimulation was commenced with gonadotrophins. The control cases were matched for female age, rank of trial, basal FSH serum concentrations and close proximity to the study group s procedure. The mean number of days of injection, the total dose of gonadotrophins used, and the number of oocytes retrieved were significantly lower in the mild stimulation group (data not shown). The mean number of embryos obtained and transferred was identical (2.0 ± 0.9 versus 2.0 ± 1.0), as the centre is obliged to inseminate only three oocytes, and the clinical pregnancy rate per embryo transfer was comparable between the two groups (31.6% versus 28.2%, in the mild and standard protocols respectively). The implantation rate, although not statistically different, was slightly higher in the study group (19.4% versus 14.8%, in the mild and standard protocols respectively) (unpublished). The particular Italian legislation cancels the possible advantages that could be derived from the use of the large number of frozen thawed embryos obtained with massive ovarian stimulation protocols, making the use of these protocols questionable until the efficacy of oocyte cryopreservation has significantly improved. However, large prospective, randomized, well-designed studies are needed to investigate this hypothesis. The mild stimulation approach might have advantages when evaluated within a given period of time. The reduced costs, the better tolerability for patients and the less time needed to complete an IVF cycle in the mild regimens could well decrease drop-out rates between cycles, thereby inducing more patients to perform more attempts, and so increase the cumulative pregnancy rates for a given period of time. To investigate this hypothesis, the clinical and cost-effectiveness implications and the patient discomfort of the mild ovarian stimulation were recently compared with conventional treatment within a year (Eijkemans et al., 2006). Moreover, with the aim of reducing multiple pregnancies and to consider a healthy baby as the only outcome measure, single and dual embryo transfer was performed in the mild and conventional stimulation groups respectively. In the mild treatment group, the mean number of started cycles was significantly higher (2.3 ± 1.2 versus 1.7 ± 1.0, P < 0.001) and the multiple pregnancy rates were significantly lower (0.5% versus 13.1%, P < 0.001). The cumulative term live birth rate after one year was comparable between the two groups (43.4% versus 44.7%, in the mild and standard protocol respectively), as was the anxiety and physical discomfort for the patients, whereas the total costs per term live birth within a year were significantly lower in the mild treatment group ( 8300 versus 10,745, P = 0.006) (Eijkemans et al., 2006). These data suggest that mild approaches are clinically and cost-effective over a given period of time. Embryo morphology is commonly used to select the best embryo for transfer and it is related to pregnancy rates but gives 677

4 678 limited information regarding the chromosomal constitution of the embryo (Munné, 2006). It has been suggested that ovarian stimulation protocols may affect embryo aneuploidy (Munné et al., 1997; Katz-Jaffe et al., 2005). Reducing the duration and intensity of the pharmacological interventions might interfere less with natural follicle selection and result in better oocyte quality with a more physiological chromosome segregation behaviour during meiosis and early embryo development. To investigate this hypothesis, very recently Baart et al. (2007) designed a prospective randomized study in which the chromosomal constitution of the embryos obtained after mild or conventional stimulation was analysed by preimplantation genetic screening in patients younger than 38 years of age. The number of oocytes retrieved and the embryos obtained were higher in the conventional stimulation group but, as previously reported (Hohmann et al., 2003), the proportion of good morphology embryos was significantly higher in the mild stimulation group (51% versus 35%; P = 0.04). Similarly, a significantly higher proportion of euploid embryos per patient (55% versus 37%; P = 0.01) and a lower proportion of mosaic embryos per patient (37% versus 65%; P = 0.004) was observed in the mild stimulation group. Within this group, a significant positive correlation was observed between the number of oocytes retrieved and the proportion of abnormal embryos (P = 0.006). On the contrary, no correlation was observed in the conventional stimulation group. These findings suggest that a reduced number of oocytes retrieved in the mild stimulation group is the result of a more physiological oocyte selection, whereas, in the conventional stimulation group, a low ovarian response is a sign of ovarian ageing (Baart et al., 2007). Natural cycles with minimal stimulation Clinical (Hohmann et al., 2003) and genetic (Baart et al., 2007) results seem to suggest that lower pharmacological interference with ovarian physiology might induce a higher proportion of developmentally competent oocytes. According to these observations, it is possible that the lower the stimulation, the better the oocyte quality obtained. Natural IVF cycle should then represent the most valid method to retrieve the best quality oocyte. Moreover, several important advantages, such as reduced costs, fewer physical (no side effects, no anaesthesia and hospital stay) and emotional burdens (less anxiety and stress as the patient does not have to worry about the ovarian response to the stimulation) are offered to the patients. However, conflicting data come from the literature regarding the efficacy of natural IVF cycles in normoresponder patients. In a review by Pelinck et al. (2002), it is possible to observe the variability of the data reported from the different published studies. The cancellation rates, the oocyte retrieval rates and the embryo transfer rates were %, 60 95% and 2480%, respectively, whereas the pregnancy rates per cycle and per embryo transfer were % and 0 50% (Daya, 1995; Zayed et al., 1997; Ingerslev et al., 2001; Nargund et al., 2001). The most important drawback of natural IVF cycles is the high cancellation rate per started cycle due mainly to an untimely LH rise (Claman et al., 1993; Lenton and Woodward, 1993). In order to reduce the incidence of premature LH surge, GnRH antagonists have been used in a single dose in the late follicular phase (Rongieres-Bertrand et al., 1999) or in a multiple dose starting when the dominant follicle has reached a diameter of 14 mm (Ubaldi et al., 2003; Pelinck et al., 2005) and obtain good clinical results. In a recent pilot study (Pelinck et al., 2005), very good implantation and pregnancy rates per transfer (32% and 36% respectively) were reported although a low pregnancy rate per started cycle (16%) due to a disappointing embryo transfer rate (44%) was observed in a group of young (<38 years of age) normoresponder patients (Pelinck et al., 2005). Similar results were obtained in the authors study centre, where 56 normoresponder, good prognosis patients underwent 151 natural IVF cycles with minimal stimulation from January 2002 to September The embryo transfer rate was 53%, the clinical pregnancy rate per embryo transfer and per cycle were 27% and 14% respectively and the implantation rate was 28%. The pregnancy rate per patient was 39%. However, for accurate assessment of the efficacy of natural IVF cycles, cumulative pregnancy rates are more useful than pregnancy rates per started cycle or per embryo transfer cycles only. Lifetime analysis from three published studies showed cumulative pregnancy rates of 43% and 42% after three and five oocyte aspirations (Paulson et al., 1992; Aboulghar et al., 1995) and 46% after four started cycles (Nargund et al., 2001). More recently, a cumulative ongoing pregnancy rate of 21% per patient after three cycles was reported (Pelinck et al., 2006). These results are encouraging especially if it is considered that natural IVF cycles are physically and probably emotionally less demanding than stimulated IVF cycles, as well as cheaper and less time consuming for laboratory and medical staff (Aboulghar et al., 1995; Nargund et al., 2001). However, no prospective randomized studies are available to assess the efficacy of natural IVF cycles with minimal stimulation compared with conventional ovarian stimulation in normoresponder patients. This minimal approach can be considered a valid alternative to massive ovarian stimulations in poor responder patients with acceptable clinical pregnancy rates (Bassil et al., 1999; Ubaldi et al., 2003; Morgia et al., 2004). On the contrary, very disappointing results were reported in the paper by Kolibianakis et al. (2004). In this latter study, the mean basal serum FSH concentration of the patients was 20 miu/ml and the oocyte retrieval was performed 32 h after HCG administration. It could be possible that selecting patients with lower serum basal FSH concentrations and postponing the oocyte retrieval could improve the oocyte quality and improve the clinical outcome. Encouraged from the acceptable results of the natural IVF cycles in poor responder patients (Bassil et al., 1999), It was decided at the authors study centre to use natural IVF cycles with minimal stimulation in poor responder patients where conventional strategies with high doses of gonadotrophins failed to obtain multiple pre-ovulatory follicles. From January 2002 to September 2006, this modified natural IVF cycle was used in 533 poor responder patients who underwent in total 962 consecutive cycles (unpublished). In this group of patients, means of 2.7 ± 1.8 ampoules of antagonist and ± IU of recombinant FSH per cycle were used. This amount of gonadotrophins is minimal compared with that used in poor responder patients after ovarian stimulation protocols. The most important drawback of this approach is the relatively low chance of performing an embryo transfer. In the authors study centre, only in 54.5% (524/962) of the started

5 cycles was it possible to obtain one embryo to transfer. The patients should be counselled and well informed about these figures. However, the cancellation rate is less dramatic because the physical, emotional and financial burdens of these couples are low and ICSI can theoretically be tried again in the next cycle. Overall, the clinical pregnancy rate observed in this group of patients was 9.9% per initiated cycle (95/962), 17.8% per patient (95/533) and 18.1% per embryo transfer (95/524) with an overall implantation rate of 17.8% (unpublished). A very important issue in favour of the natural cycle with minimal stimulation in poor responder patients is its cost effectiveness compared with the conventionally stimulated cycles. In a cost effectiveness analysis, it was calculated that a natural cycle with minimal stimulation at the authors study centre, adjusted for reductions for incomplete cycles, is costeffective compared with massive stimulation treatment cycles (Ubaldi et al., 2004). In conclusion, natural cycle IVF is a low risk and easy procedure with a pregnancy rate of about 7% per started cycle and 16% per embryo transfer (Pelinck et al., 2002). However, to assess the real efficacy of this approach in poor responder patients, large prospective randomized controlled studies are needed. Conclusions Over the last two decades, different stimulation protocols have been proposed. Easier and less expensive stimulation treatments have been largely replaced by more complex and more demanding protocols. Since the mid-nineties, the longterm GnRH agonist stimulation protocols have been widely used throughout the world. These lengthy expensive protocols have several advantages. The activity of the IVF centres can be managed more easily, the cycle cancellation rate is lower and the number of pre-ovulatory follicles is increased, thus obtaining more oocytes and good quality embryos for transfer and so leading to better pregnancy rates (Hughes et al., 1992). This should be weighted against the associated complications and costs for the patients. In fact, such ovarian stimulation protocols are not free from short- and long-term risks and negative consequences, including physical, emotional and financial burdens on patients and the ethical dilemmas about storage and disposal of extra embryos. Moreover, the greater complexity of these treatments entails weeks of daily injections, multiple blood samples and frequent ovarian ultrasound scans, that can impact on women s lives and careers. In the mild stimulation protocols, the mean number of days of stimulation and the total amount of gonadotrophins used is reduced and the mean number of oocytes retrieved is lower but the proportion of high quality embryos and euploid embryos (Baart et al., 2007) seems to be higher compared with conventional stimulation protocols whereas the pregnancy rate per embryo transfer seems to be comparable between the two approaches (Hohmann et al., 2003). Moreover, the reduced costs, the better tolerability for patients and the less time needed to complete an IVF cycle can decrease drop-out rates between cycles, inducing patients to perform more attempts and thus making mild approaches clinically and cost-effective over a given period of time (Eijkemans et al., 2006). The higher proportion of good quality and euploid embryos observed in the mild regimen groups (Hohmann et al., 2003; Baart et al., 2007) suggests that lower pharmacological interference with ovarian physiology might induce a higher proportion of developmentally competent oocytes. Milder stimulation approaches, such as natural cycle IVF with minimal stimulation, have recently been proposed as an alternative to conventional stimulation protocols in normoand poor responder patients (Ubaldi et al., 2003; Pelinck et al., 2005). Although acceptable results have been reported, further large prospective randomized studies are needed to better evaluate the efficacy of these minimal regimens compared with conventional stimulation protocols. 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