Natural cycle IVF in unexplained, endometriosis-associated and tubal factor infertility.

BACKGROUND: To elucidate possible differences between unexplained and minimal peritoneal endometriosis-associated infertility, we studied their outcome in natural cycle IVF (NIVF). METHODS: A prospective cohort study was carried out on unexplained (33 couples), minimal peritoneal endometriosis-associated (30 couples) and tubal factor (24 couples) infertility in 223 NIVF cycles, using human chorionic gonadotrophin (HCG) for ovulation induction. RESULTS: During the first NIVF attempt, follicular and luteal phase oestradiol, FSH, LH and progesterone concentrations, as well as endometrial thickness and follicular diameter were similar among the three groups. Periovulatory follicular growth monitored from day of HCG administration to oocyte aspiration was significantly lowered in unexplained infertility compared with minimal endometriosis-associated and tubal factor infertility. The fertilization rate, clinical pregnancy rate per initiated cycle, per successful oocyte retrieval and per embryo transfer, in minimal endometriosis (80.0, 10.4, 16.0 and 23.5% respectively) were similar to that in tubal factor infertility patients (68.6, 5.8, 11.4 and 16.0%) but significantly higher (P < 0.05) than that of the unexplained infertility group (62.2, 2.6, 5.4 and 8.7%). CONCLUSIONS: The significant reduction in follicular periovulatory growth, fertilization and pregnancy rates in unexplained infertility compared with minimal peritoneal endometriosis patients may be explained by sub-optimal follicular development with possibly reduced oocyte quality, intrinsic embryo quality factors or by impaired implantation. From a clinical point of view, NIVF is less suited to unexplained infertility treatment, but might represent an interesting treatment option for minimal peritoneal endometriosis-associated infertility.     

Human Fallopian tube epithelial cell co-culture increases fertilization rates in male factor infertility but not in tubal or unexplained infertility

In order to investigate the effect of human Fallopian tube epithelial cell co-culture on fertilization and cleavage rates in tubal, male and unexplained infertility, oocytes collected from 91 patients were randomized to wells containing Fallopian tube epithelial cell monolayers or conventional culture medium, and inseminated with spermatozoa. Fertilization and cleavage were assessed at 18 and 52 h, respectively. Co-culture significantly increased the fertilization rates over the control values in male infertility (41.67 versus 23.43%, P = 0.00005), but not in tubal infertility (69.33 versus 67.93%) or unexplained infertility (65.93 versus 54.36%). Cleavage rates were not different in co-culture and conventional in-vitro fertilization systems in any of the infertility subgroups. The number of blastomeres was significantly higher in the co-culture group on the day of embryo transfer (3.63 +/- 1.12 versus 3.04 +/- 1.26, P < 0.001). Pregnancy rates were similar in all infertility subgroups. There was no significant association between the number of co-cultured embryos transferred and the pregnancy, abortion and multiple pregnancy rates. It was concluded that human Fallopian tube epithelial cell co-culture clearly improves fertilization rates in male infertility but not in tubal or unexplained infertility. Improved fertilization rates in co- culture may be due to positive effect of co-culture on impaired sperm function.      

Relationship of antibodies to sperm head to etiology of infertility in patients undergoing in vitro fertilization/embryo transfer

Antibodies to sperm head (ASA-H) are believed to impair reproduction, probably because of a reduction in fertilization of human oocytes. However, the incidence of ASA-H in couples with different etiologies of infertility undergoing in vitro fertilization/embryo transfer (IVF/ET) is unestablished. To examine this question, the semen, serum, and follicular fluid of 11 couples with unexplained infertility and 25 couples with tubal infertility undergoing IVF/ET were tested with the immunobead binding assay to identify ASA-H of IgA, IgG, and IgM isotypes. Comparing couples with unexplained vs. tubal infertility, 46% vs. 4% had ASA-H of at least one isotype in female serum (P = .006), 36% vs. 4% had ASA-H in follicular fluid (P = .023), 27% vs. 0% had ASA-H in semen (P = .023), and 18% vs. 4% had ASA-H in male serum (P = .022), respectively. ASA-H were present in one or more fluids tested in 55% of patients with unexplained infertility, compared to 8% of patients with tubal infertility (P = .005). Of the six women with ASA-H in their serum, 83% (5/6) were undergoing IVF/ET for unexplained infertility compared to 17% (1/6: P = .08) undergoing IVF/ET for tubal infertility. In summary, clinically significant ASA-H are present in a substantial number of infertile women undergoing IVF/ET, particularly those whose infertility is unexplained. Based on these findings, we conclude that it is efficacious to screen all women with unexplained infertility undergoing IVF/ET for ASA-H.     

Fertilization rate in couples with unexplained infertility.

A group of 24 couples with unexplained infertility was scheduled for in-vitro fertilization and tubal embryo transfer between May 1989 and September 1990. In the same period, in-vitro fertilization and intrauterine transfer of embryos was planned in a control group of 44 women with tubal infertility. The mean age and duration of infertility were similar in both groups and the same scheme of ovarian stimulation was used. No statistically significant difference was obtained comparing oestradiol levels and numbers of mature oocytes retrieved between the group of patients with unexplained infertility and those with tubal infertility. The fertilization rate of the oocytes obtained from women with unexplained infertility (60.4%) was significantly lower (P less than 0.001) than that of the oocytes obtained from patients with tubal infertility (87.3%). There was no statistically significant difference in the cleavage rates between patients with unexplained infertility and those with tubal infertility. It is concluded that lack of fertilization is an unexplored cause of infertility in couples with unexplained infertility.     

Easily decapitated spermatozoa defect: a possible cause of unexplained infertility.

We report the first 16 cases of a new sperm abnormality which we call 'easily decapitated spermatozoa defect'. This was discovered during intracytoplasmic sperm injection (ICSI) in couples with unexplained infertility. Semen analysis was normal, but minimal micromanipulation for ICSI resulted in decapitation of the spermatozoon during immobilization. For some oocytes the head and tail were injected separately, in others the intact sperm was injected after minimal immobilization. A fertilization rate of 47.5% was obtained using ICSI. Conventional in-vitro fertilization (IVF) on sibling oocytes (three cases) or in a previous cycle (three cases) resulted in total failure of fertilization. All patients reached the embryo transfer stage and three pregnancies resulted. Findings on electron microscopy in four cases included spermatozoa with degeneration or absence of the basal plate, abnormalities of the proximal centriole and degeneration of the midpiece with a large cytoplasmic droplet. We conclude that an occult sperm abnormality presenting as easily decapitated spermatozoa during ICSI could be a cause of unexplained infertility, as it resulted in total failure of fertilization in conventional IVF. Further research is necessary to investigate this sperm abnormality.     

Defective sperm-zona pellucida interaction: a major cause of failure of fertilization in clinical in-vitro fertilization

Sperm-zona pellucida binding and penetration were assessed on the oocytes that failed to fertilize from couples with >/=3 oocytes treated by standard in-vitro fertilization (IVF). There were four groups: fertilization rate 0% (n = 369), 1-25% (n = 194), 26-50% (n = 81) and 51-95% (n = 100). Of the couples with zero fertilization rate 70% had 相似文献   

In-vitro fertilization and intracytoplasmic sperm injection in the treatment of infertility after testicular cancer

Treatment of testicular cancer (TC) may cause infertility due to reduced sperm quality with or without an ejaculation problem. In cases of anejaculation or retrograde ejaculation, spermatozoa can be obtained by transrectal electroejaculation (TE) or testicular sperm extraction (TESE) and used for in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). In this study, 15 out of 17 couples evaluated for infertility after TC, underwent a total of 21 treatment cycles, resulting in 18 embryo transfers. Spermatozoa were obtained by TE in 16 cycles, by masturbation in three cycles and by TESE in one. In one cycle no spermatozoa were found using TESE. Fertilization and cleavage was achieved by IVF in seven cycles and ICSI in 11 cycles; average fertilization rates of 57 and 55% respectively were observed. Twelve clinical pregnancies occurred, of which 11 have been delivered or are ongoing. The ongoing pregnancy rate was 57% per cycle. These results show that infertility after testicular cancer can be treated effectively with IVF and that ICSI even permits treatment of patients who have severe oligozoospermia.      

Infertility: In-vitro fertilization in completely natural cycles

Our objective was to assess the efficacy of in-vitro fertilization(IVF) in natural ovarian cycles in couples with tubal and unexplainedinfertility. A prospective study design was used. A total of39 fully investigated couples, who were patients at the ReproductiveMedicine Unit, St Michael's Hospital, Bristol, UK, took part;they were diagnosed with either tubal disease (n = 26) or unexplainedinfertility (n = 13). Procedures involved daily capillary bloodsampling, daily vaginal ultrasonography and vaginal oocyte recoveryunder sedation at mid-cycle. The main outcome measures werefertilization, implantation and pregnancy rates. Although moreof the women with tubal disease were parous, there were no othersignificant differences between the two groups. The 39 coupleswith infertility of tubal or unexplained aetiology had 79 cyclesof IVF in otherwise completely natural cycles. The overall fertilizationrate was 80% and the implantation rate was 14.0%. A trend wasobserved for higher success rates in women with tubal disease.We conclude that natural cycle IVF and embryo transfer offersan acceptable chance of pregnancy and an opportunity for thein-depth investigation of follicular and ovarian function incouples with defined causes of infertility. The possibly lowersuccess rate in women with unexplained infertility warrantsfurther study of follicular function and endocrinology.     

Should ICSI be the treatment of choice for all cases of in-vitro conception?

The objective of this study was to examine different clinical scenarios of in-vitro conception, viz. fertilization with conventional IVF, IVF with high insemination concentration (HIC) and intracytoplasmic sperm injection (ICSI), and assess on a sibling oocyte comparison the hypothesis that ICSI should be performed in all cases requiring in-vitro conception. ICSI with husband's spermatozoa had a higher incidence of fertilization as compared with IVF or IVF with HIC with donor spermatozoa (if previous failure of fertilization had occurred) for unexplained infertility. Similarly, ICSI with husband's spermatozoa had as high an incidence of fertilization as IVF with donor spermatozoa for patients with severe oligozoospermia, asthenozoospermia and/or teratozoospermia, even when the spermatozoa were not selected for their morphology. Two studies were performed to assess ICSI in potential oocyte-related failure of IVF, viz. when fertilization occurred in >50% of oocytes for one group of patients, and in <50% of oocytes in a second group. In both of these studies a significant proportion of the oocytes that failed to fertilize with conventional IVF eventually fertilized after ICSI. The overall conclusion was that ICSI as a first option offers a higher incidence of fertilization, maximizes the number of embryos and minimizes the risk of complete failure of fertilization for all cases requiring in-vitro conception. However, among other concerns, current knowledge of ICSI as an outcome procedure does not provide the confidence to use this process in all cases of IVF for the time being.     

Possibilities and limitations of techniques of assisted reproduction for the treatment of male infertility

Since relatively few spermatozoa are needed for oocyte fertilization during gamete intra-Fallopian transfer (GIFT) or in-vitro fertilization (IVF), these methods have been applied in couples with infertility due to male causes. Forty-six couples with male factor infertility were enrolled in this study and results were compared with those attained in 48 couples treated with the same techniques for other than male causes. Overall, GIFT resulted in 26% ongoing pregnancies. GIFT seems to be particularly successful when the sperm concentration is 20 x 10(6)/ml or more, but sperm motility and/or morphology are poor. Nine pregnancies occurred out of 26 GIFT cycles in 18 cases selected on this basis. The ongoing pregnancy rate after IVF was 16% per patient. The latter treatment should be attempted in male immune infertility and in cases with a low sperm concentration, with or without abnormal sperm motility and/or morphology. In these circumstances, five pregnancies were attained out of 28 cycles in 14 cases. For similar sperm concentrations, the conception rate per cycle attained with techniques of assisted reproduction was more than twice that attained with conventional treatment of male infertility.     

Sperm treatment with extracellular ATP increases fertilization rates in in-vitro fertilization for male factor infertility

Previous work from our laboratory has revealed that extracellular ATP is a rapid and potent activator of human sperm acrosome reaction and fertilizing ability. In the present study, we assessed the effects of in-vitro sperm incubation with ATP on fertilization and embryo development in couples undergoing in-vitro fertilization (IVF) for male factor infertility. Oocytes from 22 women undergoing ovulation induction were divided in two groups and inseminated in vitro either with selected spermatozoa from the corresponding partner suffering from male factor infertility pre-incubated with ATP (2.5 mM) for 1 h, or with spermatozoa incubated with 0.9% NaCl solution (control group). After insemination, fertilization was assessed by the presence of pronuclei and then by embryo cleavage. The fertilization rate in the group of oocytes inseminated with ATP-treated spermatozoa improved significantly with respect to the control group (65.7 versus 42.5%, P < 0.01). No significant differences were observed in embryo cleavage and embryo quality. Embryos from both treated and control groups were transferred together in 20 transfer procedures, and in two couples fertilization was not obtained. Nine pregnancies occurred: one biochemical, one miscarriage, and seven patients delivered 9 healthy babies. Two pregnancies were twin with an overall pregnancy rate of 40.9% per cycle and of 45% per transfer. In conclusion, the results of the present study demonstrate that, in humans, extracellular ATP induces a significant increase of sperm fertilizing potential, as these findings are a rationale for the use of ATP for in-vitro treatment of human spermatozoa during IVF.     

Treatment of severe male immunological infertility by intracytoplasmic sperm injection

A total of 29 infertile couples (group A) with male antispermantibodies detected by the mixed antiglobulin reaction (MAR)and partly by flow cytometry (n = 21) were treated using anintracytoplasmic sperm injection (ICSI) technique to assistfertilization. In all, 22 of them had shown a poor fertilizationrate (6%) in previous in-vitro fertilization (IVF) treatments.The fertilization and cleavage rates in ICSI, 79 and 89% respectively,were similar to those in a MAR-negative group (group B; n =20) injected because of male infertility (68 and 93% respectively).A third group (group C; n = 37) with male immune infertilitywas treated by conventional IVF. All these couples had at leastone oocyte fertilized, but the overall fertilization rate (44%)in group C was significantly poorer (P < 0.001) than thatin the two ICSI groups. However, the embryo quality was lowerin group A compared with that in the other groups. A total of13 pregnancies resulted in group A (46%), of which five endedin miscarriage. None of the six pregnancies (30%) in group Baborted during the first trimester. These results reveal, forthe first time, that ICSI offers a good chance of fertilizationfor couples with male immunological infertility. However, post-fertilizationevents may compromise these results because of factors not yetclearly understood.     

Andrology: Micromanipulation improves in-vitro fertilization results after epididymal or testicular sperm aspiration in patients with congenital absence of the vas deferens

In all, 58 couples suffering from infertility because of congenitalbilateral absence of the vas deferens underwent a total of 67combined microsurgical epididymal aspiration or testicular spermextraction (TESE) and in-vitro fertilization (TVT) treatments.The oocytes recovered were inseminated by either the microdropletIVF technique (n=20), subzonal insemination (SUZI; n= 10) orintracyto-plasmic sperm injection (ICSI; n= 37). Of the ICSIcycles, 12 were performed using spermatozoa obtained by TESE.Fertilization rates for epididymal spermatozoa were significantlyhigher for SUZI (17.9%, 17/95) and ICSI (34.4%, 137/398) thanfor microdroplet IVF (5.2%, 18/343) cycles. The proportion ofcycles in which fertilization was achieved was higher in theSUZI (80%) and ICSI (95%) cycles than in the IVF cycles (45%).Delivery or an ongoing pregnancy was achieved in one (5%) IVFcycle, two (20%) SUZI cycles and seven (18.9%) ICSI cycles.SUZI or ICSI using epididymal or testicular spermatozoa significantlyimproved the oocyte fertility rate. The ICSI procedure was especiallyadvantageous in patients for whom spermatozoa were obtainedfrom a testicular biopsy.     

An evaluation of couples with failure of fertilization in vitro.

Attempts at in-vitro fertilization (IVF) may be used as a method of evaluating whether in a given couple, the inability of the sperm to fertilize the oocyte may be the cause of infertility. We evaluated all IVF patients in our practice who had at least one cycle with no fertilization to determine how often this was an isolated event or was repeated in multiple cycles; would poor semen quality be found as a frequent cause; and how well can a donor sperm or oocyte 'probe' uncover which of the two is the problem? Of 35 couples who used their own gametes exclusively, 30 (85.7%) had at least one cycle with zero fertilization; 42.5% of those failing to fertilize in cycle 1 and 35% of those failing in cycle 2 had a subnormal concentration of motile spermatozoa, morphology or hypo-osmotic swelling test scores. The pregnancy rate per cycle with both husband's and wife's gametes was only 2.3% (3/130), but was 8.3% for those using donor spermatozoa (3/36) and 18.2% (2/11) for donor oocytes. Thus, failing to fertilize in a given cycle does not necessarily predict failure to fertilize in a subsequent cycle, but does predict a poor fertility outcome unless donor gametes are used.     

In-vitro fertilization in cases with severe sperm defect: use of a swim-across technique and medium supplemented with follicular fluid.

The purpose of this study was to evaluate a new method of in-vitro fertilization (IVF) in patients with severe sperm defects. Unlike the conventional swim-up method, spermatozoa and oocytes are placed in opposite corners of the bottom of the incubation dish so that sperm swimming is horizontal instead of vertical. Another difference between the swim-across and swim-up techniques is that the incubation medium is supplemented with 20% follicular fluid. After a randomized series (protocol I) of 15 IVF attempts had demonstrated that swim-across was more effective than swim-up in terms of fertilization and cleavage, we began a second series (protocol II) using only swim-across. A total of 124 couples with motile sperm counts less than 1 x 10(6) spermatozoa/ml of semen were included in protocol II. Clinical parameters (age, tubal damage) and number of recovered oocytes were recorded and compared in patients who did (group A: n = 94) and did not (group B: n = 74) achieve fertilization. In group A the fertilization rate was 36.7% and, out of the 94 transfers that were made, there were 21 clinical pregnancies and 12 full-term pregnancies with 16 live births. The number of oocytes collected (12 versus 7.7, P less than 0.001) and the incidence of tubal damage (50% versus 24.3%, P less than 0.001) was significantly higher in group A than in group B. Using logistic regression analysis, we showed a significant correlation between fertilization and progressive motility, percentage normal spermatozoa, number of recovered oocytes and tubal damage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Treatment of male infertility due to sperm surface antibodies: IUI or IVF?

This prospectively designed study was aimed at comparing the results of two different treatment protocols in 29 infertile couples with proven male immunological infertility, i.e. a positive (>50%) mixed antiglobulin reaction (MAR) test (IgG and/or IgA). In the first protocol (group I, n = 14) couples were treated with ovarian stimulation/ intrauterine insemination (IUI), followed by in-vitro fertilization (IVF) if no pregnancy occurred after three IUI cycles. In the second protocol (group II, n = 15), patients were treated with IVF as a first choice procedure. The decision to follow protocol 1 or 2 was made by the couples after information about financial costs and expected success rates (according to the literature) for both treatment options. In group I, nine patients (64.3%) conceived after a maximum of three IUI cycles whereas seven patients (46.6%) of group II became pregnant during the first IVF cycle. The take-home baby rate per started IUI or IVF cycle was 27.3% (9/33) and 44.4% (16/36) respectively with a take-home baby rate of 64.3% after three IUI cycles and 93.3% after three IVF attempts. To conclude, both IUI and IVF yielded unexpectedly high pregnancy rates in this selected group of patients with long-standing infertility due to sperm surface (predominantly IgG) antibodies. Since cost benefit analysis comparing superovulation IUI with IVF may favour a course of four IUI cycles, we advocate superovulation IUI as the first line therapy in male immunological infertility.      

Improvement of survival and fertilizing capacity of human spermatozoa in an IVF programme by selection on discontinuous Percoll gradients

Two techniques for the separation of spermatozoa were compared: swim-up migration (SUM) and centrifugation on a discontinuous Percoll gradient (CPG). Their respective effects on sperm motility were analysed by computer-assisted videomicrography in either normal or asthenozoospermic groups. In both groups, there was no difference in any of the motion parameters between the two treatments after 1-h incubation. However, a clear difference was observed after 24 h when excellent motility was retained only in the CPG-treated group. A total of 350 ejaculates were produced by the husbands of women undergoing oocyte retrieval in an IVF programme. Spermatozoa were treated by CPG when the infertility was due to poor quality spermatozoa (n = 91), when there was a known previous history of semen infection (n = 73) or when frozen semen, originating from a donor, was used (n = 36). In all other cases (n = 150), spermatozoa were treated by SUM. The cleavage rates obtained were 32.2, 70.1, 60.9 and 68.6% respectively in the four categories. The clinical pregnancy rates per oocyte retrieval were 19.8, 31.5, 22.2 and 18.0% respectively. Forty-eight births occurred in the CPG group: 28 boys and 20 girls, all normal. We conclude that CPG is useful, both in cases of poor semen quality and in tubal infertility, in which the clinical pregnancy rate increased significantly from 18.0 to 31.5%.     

Conventional in-vitro fertilization versus intracytoplasmic sperm injection in sibling oocytes from couples with tubal infertility and normozoospermic semen.

An auto-controlled study was conducted in couples with tubal infertility and normozoospermic semen. The fertilization rates and embryonic development in sibling oocytes treated, using the same semen sample, either by conventional in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) at the same time were compared. Sibling oocyte-cumulus complexes (OCC) of 56 different couples with tubal infertility and normozoospermic semen were randomly divided in order of retrieval into two groups inseminated either by conventional IVF or by ICSI. Of the retrieved OCC in the same cohort, 53.0 +/- 31.2 and 62.0 +/- 26.6% showed two distinct pronuclei after conventional IVF and ICSI respectively (not significant). Complete fertilization failure occurred after conventional IVF in 12.5% (7/56 couples). After ICSI, the comparable figure was 3.6% (2/56). The number of cases was too small to apply a statistical test to this difference. Total cleavage rates were quite similar: 86.7 +/- 28.0 and 90.1 +/- 21% of the zygotes developed into transferable embryos after IVF and ICSI respectively (not significant). Similarly, no difference in embryo quality was observed. Although injection and insemination of the oocytes were performed at the same time in the two groups, at 42 h post-insemination more embryos were at the four-cell stage after ICSI (P < 0.001) than after conventional IVF, where more embryos were still at the two-cell stage (P < 0.02). Embryo transfer was possible in all 56 couples, resulting in 16 positive serum human chorionic gonadotrophin tests (28.6% per embryo transfer), from which a clinical pregnancy resulted in 15 couples. The best embryos were selected for transfer independently of the insemination procedure, but preferably from the same origin. There appeared to be no difference in implantation potency of the embryos obtained with either technique after the non-randomized transfers.     

Results of IVF attempts in patients with unexplained infertility

From January 1986 to July 1987, 143 patients with unexplained infertility (UI) following 217 IVF attempts were studied and randomly assigned for statistical analysis to be compared with 434 tubal infertility (TI) patients undergoing 748 IVF attempts. The age of patients, previous pregnancy history and stimulation protocols were identical in both groups. In comparison with tubal patients, IVF attempts on the UI group were characterized by the same rates of cycle failure, mean number of oocytes retrieved per cycle, a lower fertilization rate (45.7% UI/59.8% TI) (P less than 0.01) and no difference in cleavage and nidation rates. However, a decrease in the pregnancy rate/attempt (13.8% UI/19.5% TI) tended towards a significant value (P = 0.06). Although the semen parameters were found to be in the normal range during the previous fertility screening in both groups, the incidence of at least one abnormality (count less than 20 X 10(6)/ml, and/or total motility less than 30% and/or abnormal forms greater than 75%) on the day of insemination was found to be significantly higher in UI (20%) than in TI (11%) patients. Moreover, 25% of UI patients did not fertilize any oocytes inseminated, whatever the number of oocytes retrieved. This rate of failed fertilization was significantly lower (9%) in tubal patients. The oestrogen response profiles were similar in both groups, analyzed according to the stimulation protocols.(ABSTRACT TRUNCATED AT 250 WORDS)     

Maturation arrest of human oocytes as a cause of infertility: case report

Maturation arrest of human oocytes may occur at various stages of the cell cycle. A total failure of human oocytes to complete meiosis is rarely observed during assisted conception cycles. We describe here a case series of infertile couples for whom all oocytes repeatedly failed to mature during IVF/ICSI. Eight couples, all presenting with unexplained infertility, underwent controlled ovarian stimulation followed by oocyte retrieval and IVF/ICSI. The oocytes were stripped of cumulus cells prior to the ICSI procedure and their maturity status was defined. In each couple, oocyte maturation was repeatedly arrested at the germinal vesicle (GV) (n = 1), metaphase I (MI) (n = 4) and metaphase II (MII) (n = 3) stage. Oocyte maturation arrest may be the cause of infertility in some couples previously classified as having unexplained infertility. The recognition of oocyte maturation arrest as a specific medical condition may contribute to the characterization of the yet poorly defined entity currently known as 'oocyte factor'. The cellular and genetic mechanisms causing oocyte maturation arrest should be the subject of further investigation.