[Autofluorescence and endometriosis optical trap or new hope in dianosis of endometriosis?].

Laparoscopic autofluorescence imaging of endometriosis is a new method to properly detect the disease. Autofluorescence in contrast to conventional white light laparoscopy enables us to visualize the entire extent of disease and to recognize extremely small or occult lesions. Autofluorescence imaging in fact reveals a world behind the world, a substantial new representation of endometriosis, which will have much impact on our future therapeutic strategies.

The use of cryopreserved mature and immature spermatozoa in assisted reproduction.

Treatment of severe male subfertility has become available since the intracytoplasmic injection of a single sperm into an oocyte was successfully applied for the first time in 1992. Moreover, with the use of fresh and cryopreserved epididymal and testicular spermatozoa for this procedure, fertilization and pregnancies could be accomplished. This review addresses the development and performance of these techniques and discusses achievements and problems as well as future aspects of the feasibility of early spermatid injection. Furthermore, limitations of these procedures and concerns with regard to genetic and epigenetic risks of using immature gametes are discussed.

Use of GnRH antagonists in the treatment of endometriosis.

Endometriosis is an oestrogen-dependent disease that is treatable by oestrogen withdrawal, a therapy that has been effectively provided by the use of a gonadotrophin-releasing hormone (GnRH) agonist. Complete oestrogen withdrawal results in unacceptable side-effects, in particular in accelerated bone density loss. This problem has been effectively overcome with 'add-back therapy' using low-dose oestrogens and progestins in combination with a GnRH agonist to limit these side-effects, while still allowing regression of endometriotic lesions. The aim of this study was to determine the feasibility of using a subcutaneous injection of GnRH antagonist in the treatment of endometriosis. All patients (15/15; 100%) reported a symptom-free period during GnRH antagonist treatment, including mood changes, hot flushes, loss of libido, vaginal dryness and other symptoms. Serum oestradiol oscillated around a mean concentration of 50 pg/ml during therapy. Diagnostic laparoscopy before GnRH antagonist administration showed a mean stage III of disease. Regression occurred in 60% of cases (9/15) and the degree of endometriosis declined to stage II. Sequential administration of the GnRH antagonist cetrorelix (Cetrotide) in a 3 mg dosage once weekly over 8 weeks creates a new opportunity for medical treatment of symptomatic endometriosis. Preserving basic oestrogen production during the course of treatment apparently does not influence regression of disease, and has no major side-effects.

Comparison of poor responders with good responders using intentionally frozen-thawed epididymal spermatozoa in subsequent ICSI cycles.

PURPOSE: To compare the outcome of intracytoplasmic sperm injection (ICSI) cycles performed with frozen-thawed epididymal spermatozoa between patients who respond poorly and patients who respond well to ovarian stimulation. METHODS: 17 patients suffering from obstructive azoospermia underwent microsurgical retrieval of epididymal spermatozoa (MESA) and the spermatozoa were frozen. The frozen-thawed spermatozoa were used in subsequent ICSI cycles. In six patients, the female partners responded poorly to ovarian stimulation. They accomplished nine ICSI cycles. In 11 patients, the female partners responded well to ovarian stimulation and they accomplished 16 cycles. RESULTS: Poor responders were older than those who reponded well. The mean number of metaphase II oocytes collected was lower in the poor responder group. In the poor responders, two couples failed to fertilise the oocytes in two ICSI cycles. In the good responders, one couple failed to fertilise the oocytes in an ICSI cycle. There were no significant differences in fertilization rates between the two groups. The estradiol concentrations on the day of hCG administration were significantly higher in the good responders. There was no pregnancy in the poor responder group, while three patients who responded well conceived. Eight good responders had 34 supernumerary 2PN oocytes which were cryopreserved. CONCLUSION: Frozen-thawed epididymal spermatozoa from men with obstructive azoospermia are potent to achieve satisfactory fertilization rates. Poor ovarian response to stimulation induction appears to be the main limiting factor in reaching the stage of embryo transfer. It is preferable in older women to cancel cycles with poor response in the hope that a better response might be obtained in a subsequent cycle. Thus, the frozen-thawed epididymal sperm can be preserved and the most stressful and expensive phase of IVF-ICSI treatment can be avoided.

High deletion frequency of the complete AZFa sequence in men with Sertoli-cell-only syndrome.

We have developed a rapid screening protocol for deletion analysis of the complete AZFa sequence (i.e. 792 kb) on the Y chromosome of patients with idiopathic Sertoli-cell-only (SCO) syndrome. This Y deletion was mapped earlier in proximal Yq11 and first found in the Y chromosome of the SCO patient JOLAR, now designated as the AZFa reference patient. We now show that similar AZFa deletions occur with a frequency of 9% in the SCO patient group. In two multiplex polymerase chain reaction experiments, deletions of the complete AZFa sequence were identified by a typical deletion pattern of four new sequence-tagged sites (STS): AZFa-prox1, positive; AZFa-prox2, negative; AZFa-dist1, negative; AZFa-dist2, positive. The STS were established in the proximal and distal neighbourhoods of the two retroviral sequence blocks (HERV15yq1 and HERV15yq2) which encompass the break-point sites for AZFa deletions of the human Y chromosome. We have found deletions of the complete AZFa sequence always associated with a uniform SCO pattern on testicular biopsies. Patients with other testicular histologies as described in the literature and in this paper have only partial AZFa deletions. The current AZFa screening protocols can therefore be improved by analysing the extension of AZFa deletions. This may provide a valuable prognostic tool for infertility clinics performing testicular sperm extraction, as it would enable the exclusion of AZFa patients with a complete SCO syndrome.

Gonadotropin-releasing hormone antagonist protocol: a novel method of ovarian stimulation in poor responders.

OBJECTIVE: To estimate the efficacy of gonadotropin-releasing hormone (GnRH) antagonist 'Cetrorelix' in poor responders comparing with the standard long protocol. DESIGN: The study population consisted of 21 poor responders who underwent ICSI and treated with Cetrorelix according to the multiple-dose protocol and who were compared with 21 poor responders treated according to the long protocol and who also underwent ICSI. Patients in both groups were matched for chronological age, the number of follicles found by ultrasound at the retrieval day and cause of infertility. Fifteen patients of GnRH antagonist group were treated with the combination of GnRH antagonist with clomiphene citrate (CC) plus gonadotropins, while six patients were treated with the combination of GnRH antagonist plus gonadotropins, but without CC. RESULTS: The use of GnRH antagonist in a multiple dose protocol gave a pregnancy rate of 14.28% which was in the range expected for patient with poor response, but with shorter treatment duration and with fewer ampoules of gonadotropins as compared with the use of a GnRH agonist protocol in a depot formulation. Within Cetrorelix group patients who received CC had a significant shorter duration of stimulation and needed fewer ampoules as compared with patients in the same group who did not receive CC. CONCLUSIONS: A GnRH antagonist multiple dose protocol may be the protocol of choice for the treatment of poor responders. The use of GnRH antagonist Cetrorelix ended with significantly less ampoules of gonadotropins and a shorter duration of stimulation.

Prospective, randomized study to evaluate the success rates using hCG, vaginal progesterone or a combination of both for luteal phase support.

BACKGROUND: A prospective study was done to compare the efficacy of luteal phase support (LPS) using either three times hCG (group I, n=77), hCG on the day of embryo transfer (ET) in combination with daily vaginal progesterone (group II, n=62) or vaginal progesterone only (group III, n=70). METHOD: All patients were treated using the long luteal protocol for controlled ovarian stimulation in an IVF (in vitro fertilization) cycle. Patients were randomized to one of these groups when estradiol was <2500 pg/ml and less than 12 oocytes were retrieved (low risk groups). If estradiol was > or = 2500 pg/ml and/or at least 12 oocytes were retrieved (high risk groups), patients were randomized to receive either hCG in combination with daily vaginal progesterone (group IV, n=83) or progesterone only (group V, n=121). For vaginal progesterone Utrogest was used (three times daily two capsules containing 100 mg progesterone, 600 mg/d). RESULTS: Demographic data were comparable within the high risk and low risk groups. However, for unknown reasons the fertilization rate was significantly higher in group V (48%) compared to group IV (40%) (p<0.05), leading to a significantly higher cumulative embryo score. There were no statistically significant differences with regard to the main outcome parameter, the clinical ongoing pregnancy rate in the low risk groups (14.3%, 14.5%, 11.4%) and the high risk groups (21.0%, 21.5%), respectively. Using a standardized discomfort scale, there were more complaints towards the end of the luteal phase in the groups receiving hCG only or an additional injection of hCG, when compared to the progesterone only groups. CONCLUSION: Progesterone only for luteal phase support leads to the same clinical ongoing pregnancy rate as hCG, but has no impact on the comfort of the patient.

Preoperative reduction of uterine fibroids in only 16 days by administration of a gonadotrophin-releasing hormone antagonist (Cetrotide).

Ten premenopausal women with symptomatic uterine fibroids confirmed by magnetic resonance imaging (MRI) were treated with four injections (s.c.) of 3 mg of the gonadotrophin-releasing hormone (GnRH) antagonist cetrorelix every 4 days, starting on the first day of cycle. On every fourth day, blood samples were drawn for the measurement of gonadotrophins and sex steroids. On the 17th day of treatment after a final MRI control, myomectomy was performed laparotomically, laparoscopically or hysteroscopically. All patients showed a deep and sustained suppression of gonadotrophins and sex steroids over the treatment time. In three patients, no change or even an increase in uterine fibroids volume was observed according to MRI, and in one patient MRI did not allow a reliable interpretation. However, six patients showed a mean reduction of 31% in fibroid size after only 16 days of hormonal treatment. In nine patients laparoscopic or hysteroscopic myomectomy could be performed, while laparotomy was necessary only in one non-responder. Preparation of the cleavage plane during surgery was easy and blood loss was minimal. Patient compliance was excellent. No side-effects occurred. The GnRH antagonist Cetrotide(R), acting as an intermediate depot preparation at a dose of 3 mg, opens up a new avenue for preoperative short term treatment in a subgroup of patients with uterine fibroids, minimizing treatment time and patient discomfort.

Preimplantation genetic diagnosis in Germany - ethical responsibility and law.

Preimplantation diagnosis (PGD) can be judged as early or brought forward prenatal diagnosis and brings up the ethical question in Germany whether potential selection of embryos and intentional killing of a human conceptus, showing a defect not or almost not compatible with life, is reconcilable with human dignity. Whereas prenatal diagnosis and its consequences are socially accepted in Germany, PGD is not compatible with the Embryo Protection Law and is still under debate since >5 years. On the other hand abortion is not subject to prosecution because the legal status of the mother outweighs that of the embryo or fetus. Here the conflict of two legally protected rights - the embryo's worth of protection and the woman's family planning - are accepted and form the basis of the potential decision of the prospective mother to carry the fetus to term or not. An obvious and deep contradiction of assessment is present between the legal requirements for the regulation of abortions in its amendment of 1995 and the Embryo Protection Law which exists unchanged since 1991. The killing of an embryo or fetus in vivo is not subject to prosecution although it is illegal, whereas the discard of an embryo in vitro after PGD was performed, also illegal, is subject to prosecution.

Outcome of ICSI cycles using frozen-thawed surgically obtained spermatozoa in poor responders to ovarian stimulation: cancellation or proceeding to ICSI?

OBJECTIVE: To investigate the ICSI outcome of the patients who produced four follicles or less after ovarian stimulation using frozen-thawed surgically obtained spermatozoa. STUDY DESIGN: The patient cohort of this study was composed of a carefully selected group of 20 men suffering from obstructive and non-obstructive azoospermia and in whom spermatozoa had been seen in their harvested epididymal aspirates and testicular tissues and the cryopreserved specimens had been used for subsequent ICSI cycles. This group of men represent those in whom the female partners produced only four follicles or less after ovarian stimulation. RESULTS: For the cases of obstructive azoospermia with MESA (n=6) a total of nine cycles was carried out. Four couples went through one cycle, one couple underwent two cycles, one couple accomplished three cycles. Out of the nine cycles, seven went to embryo transfer. No pregnancy occurred in the MESA-ICSI group of patients. The mean+/-S.D. number of oocytes per cycle was 2.556+/-1.236, the mean+/-S.D. number of embryos per transfer was 1.444+/-1.014. Two couples did not have an embryo replacement because of absence of fertilisation. The mean+/-S. D. number of gonadotropin ampoules was 53.88+/-37.30 and the mean+/-S.D. duration of ovarian stimulation was 13.38+/-4.534 days. For the cases of non-obstructive azoospermia with TESE (n=14) a total of 16 cycles was carried out. Thirteen couples went through one cycle, one couple accomplished three cycles. Out of the 16 cycles, 11 cycles went to embryo transfer. One pregnancy occurred in the TESE-ICSI group of patients, which produced live offspring. The mean+/-S.D. number of oocytes per cycle was 3.00+/-1.211, the mean+/-S.D. number of embryos per transfer was 1.313+/-1.195. Five couples did not have an embryo replacement, four of them because of absence of fertilisation and one because of abnormal fertilisation (3 PN). The mean+/-S.D. number of gonadotropin ampoules was 81. 77+/-53.40 and the mean+/-S.D. duration of ovarian stimulation was 16.71+/-3.667 days. CONCLUSION: In our opinion, these data show that it is possible to achieve satisfactory fertilisation rates using frozen-thawed epididymal and testicular spermatozoa obtained from men with obstructive or non-obstructive azoospermia, but the limiting factor in reaching the stage of embryo transfer is the poor ovarian response to stimulation induction. It therefore seems preferable to cancel these cycles, in the hope that a better response might be obtained in a subsequent cycle, avoiding in this way financial and emotional implications.

ICSI outcome in patients of 40 years age and over: a retrospective analysis.

OBJECTIVE: To report and analyse our experience with ICSI treatment in infertile women >/=40 years of age, with the intention of contributing to current debates on the effect of aging on the reproductive potential. STUDY DESIGN: 107 infertile couples in which the female partner was aged >/=40 years and who received ICSI treatment between January 1996 and December 1998. RESULTS: A total of 107 women underwent 171 treatment cycles during this period. Of 171 cycles initiated 33 were cancelled (cancellation rate=19.3%). In this way, 17 women did not have embryo transfer at all, while 90 patients had 138 cycles with oocyte retrieval and successful embryo transfer, with a mean number of embryos per transfer 2.36. Sixteen pregnancies occurred and eight of them ended in spontaneous abortion. The implantation rate was 4.9%, the pregnancy rate per initiated cycle was 9.35% and per transfer cycle 11.59%. The miscarriage rate was 50%. Moreover, 12 patients had supernumerary embryos, that were cryopreserved and transferred in 17 thawing cycles and resulted in two pregnancies ending in abortion. All pregnancies occurred when three embryos were available, except in two cases with two available embryos. The great majority of the total pregnancies (16 of 18) resulting in women aged between 40 and 42 years. CONCLUSION: Our data show that women 40 and older with existing ovarian function may benefit from ICSI treatment, even when the indication for treatment is male factor infertility. Supernumerary embryos, that are cryopreserved and transferred in subsequent cycles can improve the overall pregnancy rates per oocyte retrieval, although these women should be aware of the very high risk of miscarriage.

Use of frozen-thawed testicular sperm for intracytoplasmic sperm injection.

OBJECTIVE: To determine the feasibility of using frozen-thawed testicular spermatozoa for intracytoplasmic sperm injection. DESIGN: Prospective clinical study. SETTING: A university hospital. PATIENT(S): One hundred seventy-five azoospermic men participating in a routine intracytoplasmic sperm injection program. INTERVENTION(S): The men underwent testicular biopsy for cryopreservation of tissue to be used in consecutive intracytoplasmic sperm injection treatment cycles. Their female partners underwent controlled ovarian hyperstimulation for conventional IVF treatment. MAIN OUTCOME MEASURE(S): Fertilization and pregnancy rates. RESULT(S): In 77% of the patients, spermatozoa could be harvested from the testis by an open testicular biopsy technique and used for intracytoplasmic sperm injection after freezing and thawing of testicular tissue. Histopathologic evaluation revealed a Sertoli cell-only pattern in 21%, maturation arrest in 60%, and hypospermatogenesis in 19% of the patients. In 2. 9% of the patients, carcinoma in situ or a germ cell tumor was detected. In all patients, viable spermatozoa could be visualized after the tissue samples were thawed. One hundred thirty-five intracytoplasmic sperm injection treatment cycles were performed, with a fertilization rate of 45% and a clinical pregnancy rate of 30% per oocyte retrieved. CONCLUSION(S): The use of frozen-thawed testicular tissue allows ovarian stimulation of the female partner to be timed and avoids cancellation of ovum pick-up when spermatozoa cannot be retrieved.

[Limitations of reproduction medicine in male subfertility. Treatment of severe spermatogenesis disorders]. / Grenzen der Reproduktionsmedizin bei männlicher Subfertilität. Die Behandlung der schweren Spermatogenesestörung.

Treatment of severe male subfertility has become available since the intracytoplasmic injection of a single sperm into an oocyte was successfully applied for the first time in 1992. Moreover, also with the use of testicular spermatozoa for this procedure fertilization and pregnancies could be accomplished. This review addresses the development of these techniques and discusses achievements and problems as well as future aspects of the feasibility of early spermatid injection are stressed. Furthermore it includes the basic elements of spermatogenesis and the major concerns regarding the underlying genetic reasons for spermatogenic failure.

Genetics of male subfertility: consequences for the clinical work-up.

Major principles of genetic failures, chromosomal alterations and the most common syndromes associated with male subfertility should be taken into account before medical therapy and sophisticated techniques of assisted fertilization are applied to help a couple conceive. This review addresses the most common genetic reasons for male subfertility or infertility with special regard to the importance for the clinical work-up in daily routine and the potential risks for the conceptus.

Fertilization potential of spermatozoa with abnormal morphology.

One of the best discriminators for the fertilization potential of human spermatozoa is sperm morphology. The problem in the assessment of the sperm morphological characteristics is their pleiomorphism. Examination of spermatozoa with the light microscope can provide only limited information on their internal structure. More detailed examination of sperm structure using electron microscopy can reveal major, often unsuspected ultrastructural abnormalities. Results and cut-off values for sperm analysis depend on the criteria for normal morphology. World Health Organization recommendations provide a classification suitable for clinical practice. Clinically reliable cut-off limits for normal sperm morphology according to strict Tygerberg criteria were suggested to be 4% in in-vitro fertilization procedures. Patients with severe sperm head abnormalities have a lower chance of establishing successful pregnancies, even though fertilization may be achieved. The outcome of intracytoplasmic sperm injection is not related to any of the standard semen parameters or to sperm morphology. Sperm decondensation defects and DNA anomalies may be underlying factors for the unrecognized derangements of the fertilizing capacity of spermatozoa, regardless of sperm morphology. Centrosome dysfunction may also represent a class of sperm defects that cannot be overcome simply by the insertion of a spermatozoon into the ooplasm. In this article an overview on the composition and ultrastructure of spermatozoa is presented, while emphasizing sperm ultrastructural and sperm DNA anomalies and their effects on fertilization.

Intracytoplasmic injection of round and elongated spermatids from azoospermic patients: results and review.

Microinjection is established as the method of choice in the treatment of severe male factor infertility as well as in azoospermic patients. Recent studies have shown that fertilization and cleavage can be achieved by injection of ejaculated as well as testicular elongated spermatids into oocytes. Here we report on the two first pregnancies worldwide resulting from elongated spermatid injection from frozen-thawed testicular tissue. Four patients with complete Sertoli cell-only syndrome (SCOS) and two with spermatogenetic maturation arrest were included in our microinjection programme. Tissues from open testicular biopsies were cryopreserved until the time of follicle puncture. A total of 67 oocytes were harvested. In the two patients with maturation arrest, cryopreserved elongated spermatids were successfully injected, while in two of the other four SCOS patients only cryopreserved round spermatids were available to be injected into the oocytes. Out of 18 injected oocytes, 10 were fertilized in the first group, while nine out of 49 injected oocytes showed fertilization and cleavage in the second group. Two clinical pregnancies were achieved with elongated spermatids from frozen-thawed testicular tissue, while no pregnancy was established in the case of round spermatids. This study confirms that fertilization, cleavage and pregnancy can be successfully achieved in cases with spermatogenetic maturation arrest by injecting cryopreserved elongated spermatids into oocytes. The literature on pregnancies following spermatid injection, as well as the problems using this technique and possible risks, are discussed.

Transcervical falloscopic dilatation of proximal tubal occlusion. Is there an indication?

Proximal tubal occlusion (PTO), until recently a domain of microsurgery, can also be treated by a transcervical balloon dilatation and/or tubal recanalization. The aim of our study was to evaluate the possibility of transcervical tubal dilatation during transcervical Falloposcopy. Transcervical Falloposcopy and tubal dilatation was performed under laparoscopic control. During a period of 48 months a total of 157 Falloposcopies was performed. Out of a total of 157 patients, 42 patients had PTO confirmed by dye-pertubation during laparoscopy. All patients were referred because of primary or secondary tubal infertility. A total of 18 patients had bilateral PTO by dye-pertubation and of these six patients had successful bilateral and seven patients successful unilateral recanalization. The remaining five patients were unable to recanalize. A total of 24 patients had an unilateral PTO by dye-pertubation, 13 of these patients had a contralateral diseased tube, seven of which could be recanalized. Four patients had contralateral normal tubes, with successful recanalization in one patient. Seven patients had an occluded or missing contralateral tube, five of which could be recanalized. A total of 60 tubes with PTO were diagnosed, of which 32 (53.3%) tubes could be recanalized. 20 of these had normal tubes. Only patients with healthy Fallopian tubes carried pregnancies to term (five pregnancies, 12% of all patients). All patients conceived within a period of 3-6 months. We observed no ectopic pregnancy.

A simple, inexpensive and effective artificial cycle with exogenous transdermal oestradiol and vaginal progesterone for the transfer of cryopreserved pronucleated human oocytes in women with normal cycles.

Supernumerary pronucleated stage oocytes (PN) are usually cryopreserved. PN are transferred in spontaneous, stimulated or artificial cycles. In this study, an artificial cycle with a transdermal therapeutic system was used for oestradiol release (Estraderm TTS 100) in combination with a targeted drug delivery system for vaginal progesterone release (Crinone 8%). Patients started transdermal 17beta-oestradiol treatment on cycle day 1. Only one clinical monitoring was necessary on day 14 for confirmation of satisfactory endometrial development and exclusion of ovulation by transvaginal ultrasound and endocrine determinations (oestradiol, progesterone and luteinizing hormone). Embryo transfer was performed on the third day of progesterone treatment (day 17). The first 25 cycles were recently completed in a prospective study; no cycles were cancelled due to ovulation or unsatisfactory endometrial development. In comparison with the previous protocol of embryo transfer in stimulated cycles in our clinic which required extensive ultrasound and endocrine monitoring, the pregnancy rate in these oestrogen- and progesterone-supplemented cycles was nearly twice as high (34.8%). Two pregnancies were even achieved with zygotes after micro-injection of frozen-thawed late spermatids extracted from testicular tissue (cryo-TESE). In these cycles, the Estraderm TTS 100/Crinone 8% protocol seems to be superior to stimulation protocols and even to other protocols reported so far for artificial cycles with exogenous oestradiol and progesterone treatment.

Pregnancies achieved after frozen-thawed pronuclear oocytes obtained by intracytoplasmic sperm injection with spermatozoa extracted from frozen-thawed testicular tissues from non-obstructive azoospermic men.

The use of frozen-thawed testicular tissue as a source of spermatozoa for intracytoplasmic sperm injection (ICSI) in non-obstructive azoospermia yields favourable fertilization and pregnancy rates while avoiding both repetitive biopsies and unexpected cycle cancellations. Spermatozoa were obtained from frozen-thawed testicular biopsy specimens from 67 non-obstructive azoospermic men. Following fertilization, supernumerary two pronuclear (2PN) oocytes were frozen. After thawing, 17 cycles of embryo transfer were carried out with a mean number of 2.7 embryos and a mean cumulative embryo score (CES) of 18.3 per transfer. The clinical pregnancy and implantation rates per transfer in these cycles (23.5 and 8.3% respectively) were comparable to those of fresh embryo transfers (35.7 and 12.7% respectively) with a mean number of 2.7 embryos and a mean CES of 28.7 per transfer. Abortion rates, although higher with cryopreserved 2PN oocytes were not significantly different. With this approach, cryopreservation of supernumerary 2PN oocytes can be used to improve the cumulative pregnancy rates in a severely defective spermatogenetic population. To our knowledge, these are the first pregnancies reported which have been obtained by the transfer of cryopreserved pronuclear oocytes obtained from ICSI using cryopreserved testicular spermatozoa.

Principles of mammalian fertilization.

The principles of mammalian fertilization are defined in relation to studies of the intracytoplasmic injection of spermatozoa into human oocytes (ICSI). Sections are included on the production of mature oocytes and mature spermatozoa, sperm-oocyte interaction, and formation of the pronucleate oocyte. Current concepts in gametogenesis are discussed, including spermiogenesis, oogenesis, the biology and penetration of the zona pellucida including capacitation and the acrosome reaction, gamete fusion, the block to polyspermy and growth of the pronucleus. A concluding section relates the normal events of fertilization to those occurring after ICSI and discusses various types of anomalies found in the oocyte after ICSI.