GnRH antagonists in ovarian stimulation for IVF

The present review describes, on the basis of the currently available evidence, the consensus reached by a group of experts on the use of gonadotropin-releasing hormone (GnRH) antagonists in ovarian stimulation for IVF. The single or multiple low-dose administration of GnRH antagonist during the late-follicular phase effectively prevents a premature rise in serum luteinizing hormone (LH) levels in most women. Although controversy remains, most comparative studies suggest a slight, not significant reduction in the probability of pregnancy after IVF using GnRH antagonist versus GnRH agonist co-treatment. Published meta-analyses suggest that this slight difference in pregnancy rates is not attributed to chance. Further studies applying varying treatment regimens and outcome measures are required. Data are not in favour of a need to modify the starting dose of gonadotropins. Data are not in favour of increasing gonadotropin dose at GnRH antagonist initiation. The addition of LH from the initiation of ovarian stimulation or from GnRH antagonist administration does not appear to be necessary. Replacement of human chorionic gonadotropin (HCG) by GnRH agonist for triggering final oocyte maturation is associated with a lower probability of pregnancy. The optimal timing for HCG administration needs to be explored further. GnRH antagonist initiation on day 6 of stimulation appears to be superior to flexible initiation by a follicle of 14-16 mm, although earlier GnRH antagonist administration is worth further evaluation. Luteal phase supplementation in GnRH antagonist protocols remains mandatory in IVF. Effects of GnRH antagonist co-treatment on the incidence of ovarian hyperstimulation syndrome remains uncertain, although a trend is present in favour of the GnRH antagonists. The role of GnRH antagonists in ovarian stimulation for IVF appears to be promising, although many questions regarding preferred dose regimens and effects on clinical outcomes remain.     

Alternative approaches in IVF

Various new developments in clinical and basic science which may impact on IVF in the near or distant future will be discussed in this review. These key areas include the regulation of early follicle development and the extended in-vitro culture of oocytes and embryos. Moreover, alternative compounds and ovarian stimulation protocols will be discussed, along with highlights in the development of the cryopreservation of excess oocytes or embryos. Finally, the health economics of IVF is addressed.     

Clinical management of low ovarian response to stimulation for IVF: a systematic review

Poor response is not a rare occurrence in ovarian stimulation. Although not fully accepted, the most dominant criteria for poor ovarian response are small numbers of follicles developed or oocytes retrieved, and low estradiol (E2) levels after the use of a standard stimulation protocol. There is no ideal predictive test as the poor responder is revealed only during ovulation induction; however, increased levels of day 3 FSH and E2 as well as decreased levels of inhibin B can be used to assess ovarian reserve. Several protocols have been proposed for clinical management of low ovarian response in IVF. Although high doses of gonadotrophins have been used by the vast majority of authors, results have been controversial and prospective randomized studies have shown little or no benefit. The few available relevant studies do not indicate that recombinant FSH improves outcome. Flare-up GnRH agonist protocols (including all dosage varieties) produce better results than standard long luteal protocols. Luteal initiation GnRH agonist 'stop' protocols were shown to improve ovarian response according to prospective studies with historical controls, but this was not confirmed by well-designed prospective, randomized, controlled studies. The few available data obtained with GnRH antagonists have not shown any benefits. Adjuvant therapy with growth hormone (GH) or GH-releasing factors results in no significant improvement. The use of corticosteroids reduces the incidence of poor ovarian response in women undergoing IVF treatment. The limited data obtained with nitric oxide donors are encouraging. Pretreatment with combined oral contraceptives prior to stimulation may help ovarian response. No benefit was observed with standard use of ICSI or assisted hatching of zona pellucida. Finally, natural cycle IVF has produced results which are comparable with those obtained with stimulated cycles in true poor responders. Well-designed, large-scale, randomized, controlled trials are needed to assess the efficacy of these different management strategies.     

The use of GnRH antagonists in ovarian stimulation

GnRH antagonists induce a rapid decrease in LH and FSH, preventing and interrupting LH surges. Their properties do not require a desensitization period, and this allows their use in the late follicular phase. GnRH antagonists could replace GnRH agonists in controlled ovarian stimulation without their side-effects and their long desensitization period. Two protocols for assisted reproduction technology (ART) cycles were designed: the single-dose protocol allies simplicity and efficacy, while the multiple-dose protocol is efficient and could reduce monitoring of the cycle, though compliance is mandatory. A review of the available literature on GnRH antagonists in ART cycles is presented, focusing on phase III controlled trials and ART results. Both protocols using GnRH antagonists were associated with the need for a smaller dose of gonadotrophin, a shorter stimulation period and a lower incidence of ovarian hyperstimulation syndrome (OHSS), albeit with statistically comparable pregnancy rates. A trend is observed in all studies showing a lower pregnancy rates in GnRH antagonist cycles as compared with GnRH agonist cycles. The role of the lower number of embryos, and the potential adverse effects of GnRH antagonists on endometrium or follicle must be studied. More cycles using GnRH antagonists are necessary to confirm their equivalent pregnancy rates. There is room for improvement in both protocols with regard to scheduling, antagonist dose level and the timing of its administration. Until further studies have been conducted, luteal support seems to remain mandatory. Perinatal outcome appears similar to that with other stimulation regimens. Triggering of ovulation can be obtained with GnRH agonist for patients at risk of OHSS. With regard to GnRH antagonists, questions remain regarding pregnancy rates, the indications of their use in patients with polycystic ovary syndrome or poor responders, and in ovarian stimulation outside IVF.     

A systematic review of tests predicting ovarian reserve and IVF outcome

The age-related decline of the success in IVF is largely attributable to a progressive decline of ovarian oocyte quality and quantity. Over the past two decades, a number of so-called ovarian reserve tests (ORTs) have been designed to determine oocyte reserve and quality and have been evaluated for their ability to predict the outcome of IVF in terms of oocyte yield and occurrence of pregnancy. Many of these tests have become part of the routine diagnostic procedure for infertility patients who undergo assisted reproductive techniques. The unifying goals are traditionally to find out how a patient will respond to stimulation and what are their chances of pregnancy. Evidence-based medicine has progressively developed as the standard approach for many diagnostic procedures and treatment options in the field of reproductive medicine. We here provide the first comprehensive systematic literature review, including an a priori protocolized information retrieval on all currently available and applied tests, namely early-follicular-phase blood values of FSH, estradiol, inhibin B and anti-Müllerian hormone (AMH), the antral follicle count (AFC), the ovarian volume (OVVOL) and the ovarian blood flow, and furthermore the Clomiphene Citrate Challenge Test (CCCT), the exogenous FSH ORT (EFORT) and the gonadotrophin agonist stimulation test (GAST), all as measures to predict ovarian response and chance of pregnancy. We provide, where possible, an integrated receiver operating characteristic (ROC) analysis and curve of all individual evaluated published papers of each test, as well as a formal judgement upon the clinical value. Our analysis shows that the ORTs known to date have only modest-to-poor predictive properties and are therefore far from suitable for relevant clinical use. Accuracy of testing for the occurrence of poor ovarian response to hyperstimulation appears to be modest. Whether the a priori identification of actual poor responders in the first IVF cycle has any prognostic value for their chances of conception in the course of a series of IVF cycles remains to be established. The accuracy of predicting the occurrence of pregnancy is very limited. If a high threshold is used, to prevent couples from wrongly being refused IVF, a very small minority of IVF-indicated cases (approximately 3%) are identified as having unfavourable prospects in an IVF treatment cycle. Although mostly inexpensive and not very demanding, the use of any ORT for outcome prediction cannot be supported. As poor ovarian response will provide some information on OR status, especially if the stimulation is maximal, entering the first cycle of IVF without any prior testing seems to be the preferable strategy.     

Cellular and molecular aspects of ovarian follicle ageing

It is well established that age-related decline of the biological capacity of a woman to reproduce is primarily related to the poor developmental potential of her gametes. This renders female ageing the most significant determinant of success in IVF. Starting with a reference picture of the main molecular and cellular failures of aged oocytes, granulosa cells and follicular microenvironment, this review focuses on age-related biochemical mechanisms underlying these changes. According to the most relevant concept of ageing, age-associated malfuction results from physiological accumulation of irreparable damage to biomolecules as an unavoidable side effect of normal metabolism. More than a decade after the free radical theory of ovarian ageing, biological and clinical research supporting the involvement of oxidative injuries in follicle ageing is discussed. Looking for the aetiology of oxidative stress, we consider the effect of ageing on ovarian and follicular vascularization. Then, we propose a potential role of advanced glycation end-products known to be involved in the physiological ageing of most tissues and organs. We conclude that future investigation of age-related molecular damage in the different ovarian components will be imperative in order to evaluate the possibility to save or rescue the developmental potential of aged oocytes.     

Regulation of primordial follicle assembly and development

The assembly of the primordial follicles early in ovarian development and the subsequent development and transition of the primordial follicle to the primary follicle are critical processes in ovarian biology. These processes directly affect the number of oocytes available to a female throughout her reproductive life. Once the pool of primordial follicles is depleted a series of physiological changes known as menopause occur. The inappropriate coordination of these processes contributes to ovarian pathologies such as premature ovarian failure (POF) and infertility. Primordial follicle assembly and development are coordinated by locally produced paracrine and autocrine growth factors. Endocrine factors such as progesterone have also been identified that influence follicular assembly. Locally produced factors that promote the primordial to primary follicle transition include growth factors such as kit ligand (KL), leukaemia inhibitory factor (LIF), bone morphogenic proteins (BMP's), keratinocyte growth factor (KGF) and basic fibroblast growth factor (bFGF). Factors mediating both precursor theca-granulosa cell interactions and granulosa-oocyte interactions have been identified. A factor produced by preantral and antral follicles, Müllerian inhibitory substance, can act to inhibit the primordial to primary follicle transition. Observations suggest that a complex network of cell-cell interactions is required to control the primordial to primary follicle transition. Elucidation of the molecular and cellular control of primordial follicle assembly and the primordial to primary follicle transition provides therapeutic targets to regulate ovarian function and treat ovarian disease.     

The clinical significance of the retrieval of a low number of oocytes following mild ovarian stimulation for IVF: a meta-analysis

BACKGROUND: Milder ovarian stimulation protocols for in vitro fertilization(IVF) are being developed to minimize adverse effects. Mildstimulation regimens result in a decreased number of oocytesat retrieval. After conventional ovarian stimulation for IVF,a low number of oocytes are believed to represent poor ovarianreserve resulting in reduced success rates. Recent studies suggestthat a similar response following mild stimulation is associatedwith better outcomes. METHODS: This review investigates whether the retrieval of a low numberof oocytes following mild ovarian stimulation is associatedwith impaired implantation rates. Three randomized controlledtrials comparing the efficacy of the mild ovarian stimulationregimen (involving midfollicular phase initiation of FSH andGnRH co-treatment) for IVF with a conventional long GnRH agonistco-treatment stimulation protocol could be identified by meansof a systematic literature search. RESULTS: These studies comprised a total of 592 first treatment cycles.Individual patient data analysis showed that the mild stimulationprotocol results in a significant reduction of retrieved oocytescompared with conventional ovarian stimulation (median 6 versus9, respectively, P < 0.001). Optimal embryo implantationrates were observed with 5 oocytes retrieved following mildstimulation (31%) versus 10 oocytes following conventional stimulation(29%) (P = 0.045). CONCLUSIONS: The optimal number of retrieved oocytes depends on the ovarianstimulation regimen. After mild ovarian stimulation, a modestnumber of oocytes is associated with optimal implantation ratesand does not reflect a poor ovarian response. Therefore, thefear of reducing the number of oocytes retrieved following mildovarian stimulation appears to be unjustified.     

The endometrium in stimulated cycles for IVF

Ovarian stimulation for IVF is known to affect luteal phase function. The endometrium in IVF cycles is thus subject to an altered endocrinological environment and to a possible direct effect of the ovarian stimulation therapy. Factors influencing the endometrial receptivity in such cycles are poorly understood. Studies comparing the endometrium in IVF cycles with natural cycles as controls have shown premature secretory changes in the post-ovulatory and early luteal phase of IVF cycles, followed by a large proportion of dyssynchronous glandular and stromal differentiation in the mid-luteal phase. These findings suggest a profound modification of luteal endometrial development in stimulated cycles. This hypothesis is further supported by the demonstration of a modified endometrial steroid receptor regulation and a profound antiproliferative effect in IVF cycles. The time of maximal endometrial receptivity is defined as the implantation window and is characterized by the expression of various endometrial products, among which pinopodes, integrins and leukaemia inhibitory factor are best described. Premature expression of pinopodes and integrins are in line with the observation of precocious luteal transformation following ovarian stimulation, although the clinical relevance with respect to the establishment of a clinical pregnancy awaits further validation. Studies exploring the endometrium within the cycle of embryo transfer have shown a deleterious effect of severe peri-ovulatory maturation advancement exceeding 3 days, as no clinical pregnancies were obtained in this condition. Further unravelling of molecules involved in the implantation mechanism is needed for a better comprehension of the link between altered endometrial development and receptivity in IVF cycles.     

Ovarian stimulation and ovarian tumours: a critical reappraisal

Increased interest has arisen recently about the possible associationbetween ovarian stimulation and ovarian tumours. In this article,the current knowledge on the epidemiology, pathogenesis andaetiology of ovarian tumours is extensively reviewed in relationto the existing literature on the relationship between ovulationinduction and ovarian neoplasia. The available data from epidemiologicalstudies and case reports do not support a direct causa] relationshipbetween ovarian stimulation and ovarian cancer. However, itis possible that ovarian stimulants may have an augmenting rolefor special categories of tumours, e.g. sex-cord stromal tumours.A definite answer to this important issue may be reached throughlarge prospective epidemiological studies or large retrospectivewell-designed case-control studies.     

Ovarian follicle development and transgenic mouse models

Ovarian follicle development is a complex process that beginswith the establishment of what is thought to be a finite poolof primordial follicles and culminates in either the atreticdegradation of the follicle or the release of a mature oocytefor fertilization. This review highlights the many advancesmade in understanding these events using transgenic mouse models.Specifically, this review describes the ovarian phenotypes ofmice with genetic mutations that affect ovarian differentiation,primordial follicle formation, follicular growth, atresia, ovulationand corpus luteum (CL) formation. In addition, this review describesthe phenotypes of mice with mutations in a variety of genes,which affect the hormones that regulate folliculogenesis. Becausestudies using transgenic animals have revealed a variety ofreproductive abnormalities that resemble many reproductive disordersin women, it is likely that studies using transgenic mouse modelswill impact our understanding of ovarian function and fertilityin women.     

An improved use of buserelin in ovarian stimulation for in-vitro fertilization

In earlier IVF programmes, subcutaneous buserelin (Suprefact, Hoechst) was initially administered three times per day (200 micrograms x 3); then twice daily (300 micrograms x 2). We now suggest that a single administration of 600 micrograms daily may be equally effective. In a preliminary study, 20 patients were selected on the basis of tubal or idiopathic infertility and received 0.6 ml buserelin subcutaneously once a day, beginning on day 1 or 2 of the cycle. A sufficient pituitary desensitization was obtained on day 10 in 75% of patients and on day 16 for 100% and the ongoing pregnancy rate was 35% per treatment cycle. A randomized study comparing the effect of 600 micrograms of buserelin administered in one (n = 50) or two injections (n = 46), has been carried out and indicates that the results in terms of the ovarian suppression and pregnancy rates, were similar. Therefore, this protocol represents a simplification of the treatment with buserelin.     

Predictors of low response to mild ovarian stimulation initiated on cycle day 5 for IVF

BACKGROUND: Milder stimulation protocols are being developed to minimize adverse effects of ovarian stimulation in in vitro fertilization (IVF) programs. A drawback is the possibility of an increased rate of insufficient ovarian response. This study aimed to develop a prognostic model for the prediction of cycle cancellation due to insufficient response to mild stimulation. METHODS: A total of 174 IVF patients aged<38 years and with a body mass index (BMI)<28 Kg/m2 were treated with mild ovarian stimulation using a fixed daily dose (150 IU) of recombinant follicle-stimulating hormone (rFSH) from cycle day 5 and GnRH antagonist from the late follicular phase. In women with mono- or bifollicular growth (17%), the cycle was cancelled and the treatment was adjusted in a second treatment cycle by starting rFSH on cycle day 2. RESULTS: In a multivariable logistic regression analysis, duration of infertility, menstrual cycle length, secondary infertility and BMI were included in the prediction model. The area under the receiver-operating characteristics curve of the model was 0.69. A probability cut-off for cancellation of 0.3 yielded an expected sensitivity of 33% and specificity of 92%. Analysis of ovarian response in the subsequent treatment cycle showed an improved ovarian response and a significant reduction in the cancellation rate. CONCLUSIONS: With the presented model, it is possible to identify patients at risk for cycle cancellation, during mild ovarian stimulation, due to insufficient response. The contributing factors of the model suggest that ovarian aging and BMI are related to insufficient response to mild stimulation.     

The effect of an individualized GnRH antagonist protocol on folliculogenesis in IVF/ICSI

BACKGROUND: The aim of this study was to assess the effect of an individualized GnRH antagonist regimen on folliculogenesis. METHODS: In a multicentre, randomized, clinical trial, IVF/ICSI patients were allocated to a standard regimen, in which they received daily 0.25 mg GnRH antagonist ganirelix (Orgalutran) from the 6th day of stimulation onward (fixed regimen n = 102) or to an individualized regimen, in which IVF/ICSI patients received daily 0.25 mg GnRH antagonist starting on the day that the dominant follicle had reached a diameter of > or = 15 mm (flexible regimen n = 103). The primary endpoint was to assess the difference in the total number of oocytes. RESULTS: The mean (SD) number of retrieved oocytes was not statistically significantly different: 9.4 (5.8) in the flexible group versus 9.7 (6.5) in the fixed group. The clinical and ongoing pregnancy rates were 22.7 and 21.8% respectively in the flexible group versus 33 and 31.1% in the fixed group [relative rate ratio 0.69 (95% confidence interval 0.44-1.08) and 0.7 (0.44-1.12) respectively]. CONCLUSION: The individualized flexible regimen did not result in an increase in the total number of oocytes obtained.     

A prospective, randomized comparison of two starting doses of recombinant FSH in combination with cetrorelix in women undergoing ovarian stimulation for IVF/ICSI

BACKGROUND: A prospective randomized study was carried out in two centres to compare the number of oocytes retrieved after two different starting doses of recombinant human FSH (rhFSH) (Gonal-F) in women undergoing ovarian stimulation for IVF/intracytoplasmic sperm injection (ICSI) cycles using the multiple dose regimen of the gonadotrophin-releasing hormone (GnRH) antagonist cetrorelix (Cetrotide) to prevent induction of the premature LH surge. METHODS: Sixty women were randomized to receive rhFSH 150 IU ('low'), and 60 women to receive rhFSH 225 IU ('high') as the starting dose for the first 5 days of stimulation. From stimulation day 6 and onwards, including the day of human chorionic gonadotrophin (HCG) administration, the women received 0.25 mg of cetrorelix as a daily dose. The primary endpoint was the number of oocytes retrieved. RESULTS: The mean number (+/- SD) of oocytes was 9.1 +/- 4.4 and 11.0 +/- 4.6 in the 'low' and 'high' groups respectively (P = 0.024). The mean number of 75 IU ampoules of rhFSH was significantly lower in the 'low' group (23.0 +/- 6.3 versus 30.5 +/- 5.6, P < 0.0001). The ongoing pregnancy rate per started cycle and per embryo transfer were 25.9 and 28.8% versus 25.4 and 26.8% respectively in the 'low' and 'high' rhFSH groups (P = NS). CONCLUSIONS: When using a starting dose of 225 IU rhFSH combined with the multiple dose of 0.25 mg cetrorelix from stimulation day 6, significantly more oocytes were obtained than with a starting dose of 150 IU rhFSH.     

The ISMAAR proposal on terminology for ovarian stimulation for IVF

IVF is performed with oocytes collected in natural and stimulated cycles. Different approaches to ovarian stimulation have been employed worldwide. Following the introduction of GnRH antagonists and strategies to reduce multiple births such as single embryo transfer, there is a genuine scientific interest in the revival of natural cycle and mild approaches to ovarian stimulation in IVF. Recent evidence suggests that application of natural and mild IVF is patient-centred, aimed at reducing the cost of treatment, patient discomfort and multiple pregnancies. However, there seems to be no consistency in the terminology used for definitions and protocols for ovarian stimulation in IVF cycles. Following the recent International Society for Mild Approaches in Assisted Reproduction (ISMAAR) meeting and communication with interested international experts, this article has recommended revised definitions and terminology for natural cycle IVF and different protocols used in ovarian stimulation for IVF. It is proposed that these terms are adopted internationally in order to achieve a consistency in clinical practice, research publications and communication with patients.     

How to make a good oocyte: an update on in-vitro models to study follicle regulation

The ability to develop the technology to mature oocytes from immature oocytes in vitro is the ambition of many IVF clinics. If this can be successfully achieved then these techniques would be available to women with fertility problems. This would aid women at risk of premature ovarian failure, and possibly result in women no longer requiring an expensive drug regime and monitoring programme, which they currently have to undergo. The idea of harvesting immature oocytes for growth in vitro is not a new one, but progress has been slow in developing and optimizing techniques for use on humans and domestic species. At present, there are many technical reasons for the lack of progress in these species, such as length of culture and difficulty of follicle isolation. However, the major problem is our lack of knowledge of how the oocyte acquires developmental competence during its growth within the follicle. To date, culture systems have been developed that can support the growth and development of immature oocytes. These systems are beneficial in improving our knowledge of how autocrine/paracrine factors are involved in regulating and controlling oocyte development. However, only when we have a more in-depth understanding of what is required during development to make a viable oocyte, will we perhaps be able to develop in-vitro culture systems for clinical application. This review will focus on how analysis of early follicular growth and development, using in-vitro culture systems, has advanced our knowledge of the factors and process involved in the regulation of oocyte and somatic cell development.     

Short-term use of buserelin in combination with human menopausal gonadotrophins for ovarian stimulation for in-vitro fertilization in endocrinologically normal women

Ten endocrinologically normal women were injected subcutaneously with 500 micrograms D-Ser(TBU)6-EA10-LHRH (buserelin) on days 3,4 and 5 after the start of the menses. Two types of response were observed. Five women (group A) responded promptly and had a mean number of 13.4 oocytes retreived after 11.4 days of stimulation. In the second group (B), two to three times more HMG was needed to obtain a mean number of 7.3 oocytes after 17.2 days of stimulation. The response upon stimulation could be predicted by the serum gonadotrophin output on days 4 and 5 of the cycle. One woman from group B had a premature LH rise on day 16 and luteinization; her cycle was abandoned. In the four other patients of group B, serum and urinary LH concentrations showed that pituitary gonadotrophin secretion had recovered before the ovulatory stimulus, without signs of premature luteinization. Two women in each group became pregnant, one of whom aborted. This short-term GnRH agonist treatment could be an alternative method for ovarian stimulation, although it did not totally prevent the occurrence of an endogenous LH surge.     

The influence of hydrosalpinx on IVF and embryo transfer: a review

Several retrospective studies have shown an impaired outcomeof IVF in the presence of hydrosalpinx. The retrospective datahave been compiled and presented in meta-analyses, demonstratinga reduction by half in the probability of achieving a pregnancyin the presence of hydrosalpinx and a doubled rate of spontaneousabortion. The main theories trying to explain the underlyingmechanisms have focused on potential embryotoxic propertiesof the fluid or impaired endometrial receptivity to implantation.Several mouse studies have suggested an embryotoxic effect ofthe hydrosalpingeal fluid, a finding which is not supportedin studies on human embryos. It is believed that the fluid exertsa detrimental effect on the endometrium by altering the receptivityor simply by causing a mechanical hindrance for implantation.Different treatment options would then be tubal ligation, salpingostomy,aspiration of hydrosalpinx fluid or salpingectomy. The effectof aspiration has been studied in a few retrospective trialswith contradictory results. Treatment with salpingectomy hasentered into clinical practice without proper evidence for itsbenefit. Concerns have also been raised about the potentialhazard of surgical intervention to ovarian circulation and function.A randomized controlled trial on salpingectomy prior to IVFhas now been conducted as a multicentre study in Scandinavia.Laparoscopic salpingectomy prior to IVF was shown to be beneficialin patients with large hydrosalpinges that were visible on ultrasound,a result which supports the theory of the fluid being involvedin the impaired implantation process.     

Perinatal outcome and developmental studies on children born after IVF

Since the first birth after IVF, many scientific papers have been published on the technical aspects of the IVF procedure, but few studies have addressed the issue of the perinatal outcome of IVF pregnancies and of the children's development and well-being. A high rate of adverse outcome has been demonstrated in a large group of IVF pregnancies. Prematurity, low birth weight and perinatal mortality are higher than in the general population. The majority of these complications are related to multiple births, but they are also found in singleton pregnancies. An analysis of the multiple risk factors involved in these complications is needed. The infertile status of IVF patients clearly plays a role in the risk of adverse outcome. Age and parity may be important factors. The role of IVF itself has not been demonstrated convincingly. The effect of ovarian stimulation deserves further study. Most of the studies published on the follow-up of IVF children are reassuring, but it is clear that these studies are not sufficient to eliminate without doubt any adverse effects on the well-being of IVF children. All IVF pregnancies should be followed with great care, not because they are more precious than spontaneous pregnancies, but because they are exposed to an increased risk of complications. The main problem of IVF remains the high rate of multiple pregnancies, including twins.