Journal of Andrology
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Journal of Andrology, Vol. 27, No. 1, January/February 2006
Copyright © American Society of Andrology
DOI: 10.2164/jandrol.05076

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Analysis of Outcomes of Cryopreserved Surgically Retrieved Sperm for IVF/ICSI

MOSHE WALD*, LAWRENCE S. ROSS*, GAIL S. PRINS*, JEANINE CIESLAK-JANZEN{dagger}, GEORG WOLF{dagger} AND CRAIG S. NIEDERBERGER*

From the * Department of Urology, the University of Illinois at Chicago, Chicago, Illinois; and the {dagger} Reproductive Genetics Institute, Chicago, Illinois.

Correspondence to (current address): Dr Moshe Wald, University of Iowa, Department of Urology, 200 Hawkins Drive, 3 RCP, Iowa City, IA 52242-1089 (e-mail: moshe-wald{at}uiowa.edu).
Received for publication April 12, 2005; accepted for publication July 14, 2005.

   Abstract
Top
 Abstract
Materials and Methods
 Results
 Discussion
 References
 
We evaluated our experience to date with in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) after either cryopreserved sperm or sperm produced on the date of IVF/ICSI was used. We performed a retrospective statistical analysis of data derived from 188 women undergoing IVF/ICSI cycles using surgically retrieved sperm. A total of 318 IVF/ICSI treatment cycles with 3280 ova were performed using testicular sperm extraction (TESE, 304 cycles) or microsurgical epididymal sperm aspiration (MESA, 14 cycles). Sperm obtained at time of IVF/ICSI (fresh) or thawed cryopreserved sperm samples were used in 38 and 280 of the ICSI cycles, respectively. For IVF/ICSI cycles using both TESE and MESA sperm, the fertilization rate was 59.9% for cryopreserved sperm, and 53.6% when fresh sperm was used ({chi}2 P-{alpha} < .02, Cramer's {phi} 0.04). The fertilization rate for the TESE group alone was 60.0% for cryopreserved sperm and 55.1% for fresh sperm ({chi}2 P-{alpha} = .075). Cohen effect size was computed at 0.03; yielding for P-ß = .8, 6597 ova would be required to demonstrate similarity between fresh and cryopreserved sperm in the TESE group. To demonstrate superiority of cryopreserved sperm in this group at a P-{alpha} significance level of .05, 7524 ova would be necessary. The pregnancy rate for the TESE group was 27.3% for cryopreserved sperm and 27% for fresh sperm. Further analysis of the pregnancy data in this group, using the methods described, yielded a {chi}2 P-{alpha} and power of 0.971 (effect size calculated at 0.002). While our fertilization rates for cryopreserved sperm are greater in analyses of surgically derived sperm, based on the 7 years required to obtain data on 3280 ova, full numerical resolution of the issue of whether cryopreserved sperm is superior or similar will not be available until approximately 2010. However, we believe these results, along with the similarity shown in pregnancy rates achieved with both types of sperm, clearly indicate that cryopreserved sperm is not inferior to fresh sperm.

     Key words: Pregnancy, spermatozoa, fertilization, cryopreservation, reproductive techniques


The introduction of intracytoplasmic sperm injection (ICSI), requiring only 1 sperm for achieving fertilization with a subsequent transferable embryo and clinical pregnancy has revolutionized the treatment of male infertility (Palermo et al, 1992). This technique, coupled with in vitro fertilization (IVF), enables men whose infertility was previously considered as uncorrectable to father a biological offspring. This has changed the nature of testicular reproductive interventions, adding therapeutic options to the traditional diagnostic testicular biopsy. Standard testicular sperm extraction (TESE), alone or combined with vasal reconstructive procedures, as well as percutaneous or microsurgical epididymal sperm aspiration (MESA) have been shown as efficient and reliable methods for sperm retrieval in patients with obstructive azoospermia (OA) in whom assisted reproductive techniques (ART) are planned (Nudell et al, 1998). However, as spermatogenesis is impaired in men with nonobstructive azoospermia (NOA), sperm retrieval rates have been reported to be only 36%-64% if standard TESE is performed (Schlegel et al, 1997; Palermo et al, 1999; Prins et al, 1999). Several microsurgical methods have been suggested to address this problem (Schlegel 1999; Turek et al, 2000). Microdissection TESE has been reported to provide better sperm retrieval through smaller volumes of testicular tissue removed, as compared with standard biopsies, with the additional advantage of identification and preservation of the subtunical vessels, potentially lowering the risk of testicular function impairment, observed in larger volume standard testicular biopsies (Manning et al, 1998; Schlegel, 1999).

The use of surgically retrieved fresh and cryopreserved sperm for assisted reproduction has been studied in recent years, but uncertainty still exists concerning the possible superiority of 1 of these sperm-handling methods. Table 1, which summarizes recent data concerning IVF/ICSI outcomes of cryopreserved versus fresh sperm, shows overall comparable fertilization rates (39.0%-61.7% and 47.0%-61.9%, respectively) and clinical pregnancy rates (20%-41% and 23%-33%, respectively) reported for frozen-thawed and fresh sperm (excluding the study of Romero et al, which reported only on 2 cases). High fertilization and pregnancy rates were reported in IVF/ICSI treatments using fresh sperm obtained by TESE, in both OA and NOA patients (Devroey et al, 1995; Silber et al, 1995, 1996). While some authors reported fertilization and/or pregnancy rates to be lower with frozen-thawed sperm as compared with fresh, others demonstrated similar IVF/ICSI outcomes for both sperm-handling methods (Gil-Salom et al, 1996; Romero et al, 1996; Friedler et al, 1997; Verheyen et al, 1997; Palermo et al, 1999; Prins et al, 1999; Habermann et al, 2000). We evaluated our experience to date with IVF/ICSI after either fresh or cryopreserved sperm was used.


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  		Table 1. IVF/ICSI outcomes with frozen-thawed and fresh sperm (summary of previously published series)
 


   Materials and Methods
Top
 Abstract
 Materials and Methods
Results
 Discussion
 References
 
We retrospectively analyzed a dataset derived from patients undergoing IVF/ICSI cycles using fresh and/or cryopreserved surgically retrieved sperm at a single IVF center. Between February 1996 and July 2003, a total of 318 IVF/ICSI treatment cycles with 3280 ova were performed in 188 women, aged 22-44 years (mean 33). Sperm was retrieved by TESE or MESA, in 304 and 14 of the ICSI treatment cycles, respectively. Sperm obtained at time of IVF/ICSI (fresh) or thawed cryopreserved sperm samples were used in 38 and 280 of the ICSI cycles, respectively. This series includes data previously reported by our group (Prins et al, 1999).

Institutional Review Board (IRB) approval was not obtained for this study because data were collected via retrospective chart review without disclosure of patient identification. In addition, the study analyzes a well-established clinical therapeutic procedure that is not experimental and is not under IRB guidance.

Maternal age at the time of oocyte retrieval, IVF/ICSI characteristics (number of cycles, number of oocytes retrieved, number of mature oocytes, embryos transferred), and outcomes (fertilization and implantation rates, numbers of biochemical pregnancies, miscarriages, ectopic pregnancies, and live births) were compared between fresh and cryopreserved sperm in all cycles and in the subsets of IVF/ICSI cycles using epididymal and TESE sperm (Table 2). Pregnancy rates were also analyzed in the latter group. Statistical analysis was performed using standard chi-square and power per Cohen (Cohen, 1988).


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  		Table 2. Comparison of ICSI cycles using fresh and frozen sperm
 

Surgical Sperm Retrieval

TESE was performed either in the standard fashion or using the microdisection technique described by Schlegel (1999). Standard TESE involved a midline scrotal incision, through which a window was created in the tunica vaginalis to expose the tunica albuginea. Testicular tissue was then expressed, observed, and sampled through a 0.5-1.0-cm incision in the tunica albuginea. If needed, further samples were obtained. The tunica albuginea, tunica vaginalis, dartos, and skin were then closed in separate layers.

MESAs were performed according to the technique of Schlegel et al (1994).

Sperm Cryopreservation

The TESE specimen was placed in a Petri dish with human tubal fluid (HTF)+HEPES supplemented with 0.3% bovine serum albumin (BSA) at 37°C. Under a dissecting microscope, the seminiferous tubules were teased apart using 21-gauge needles, and the contents were squeezed into the surrounding media. The tubules were transferred to a 15-mL conical tube containing 1 mL of fresh media, and the cell suspension was transferred to a separate centrifuge tube. Both tubes were incubated at 37°C for 15-30 minutes, and the supernatant of the first tube (containing tubules) was combined with the cell suspension in the second tube. The suspension was centrifuged at 500 x g for 5 minutes, and the pellet was resuspended in 1 mL Ham F-10 with 0.3% BSA. A cell count was performed, and the suspension was diluted or concentrated to 0.5-1.0 million sperm/mL. Before freezing, an aliquot was removed to assess sperm quality. At cryopreservation, multiple aliquots of sperm were frozen whenever possible. The cell suspension was slowly diluted 1:1 with TEST-citrate-yolk buffer with 12% glycerol so that the final concentration of glycerol was 6%. The samples were slow-cooled at a rate of -0.5°C/min to 4°C and then packaged in 1-mL cryovials (Nunc, Denmark). The vials were frozen at a rate of -10°C/min to -90°C and were stored in liquid nitrogen at -196°C.

Sperm obtained through MESA was aspirated into culture medium. It was frozen just as native semen in TESTyolk buffer and glycerol (Irvine Scientific, Irvine, Calif).

Ovarian Stimulation, Sperm Thaw, and ICSI

Ovarian stimulation was achieved using a standard long protocol consisting of down-regulation with GnRH agonist (Lupron, Tap Pharmaceutical, Deerfield, Ill) in the preceding cycle followed by controlled ovarian hyperstimulation with either hMG or FSH during the treatment cycle. Serum estradiol levels and follicular growth were monitored periodically. When the mean follicular diameter of 2 leading follicles reached approximately 18 mm, hCG was administered. Oocyte retrieval through transvaginal ultrasound puncture was performed approximately 35 hours post-hCG administration.

Oocytes were cultured in HTF medium supplemented with Plasmanate (Bayer Biological, West Haven, Conn) at 37°C under 5% CO2. The cumulus-corona complex was removed by pipetting after a short exposure to hyaluronidase (Type VIII; Sigma, St Louis, Mo), and the oocytes were returned to culture. A vial of frozen sperm was thawed at room temperature for 10 minutes for a minimum of 4 hours before ICSI and, in some cases, as early as the evening before the retrieval. After thaw, sperm samples were washed in HTF culture medium (Irvine Scientific), supplemented with Plasmanate (plasma protein—Bayer Biological) 5% volume: volume, and centrifuged at 300 x g for 10 minutes. The supernatant was removed, and the pellet was resuspended in HTF medium with 1% HSA. The sperm were cultured at 37°C until used for ICSI. In most cases, viable sperm began to twitch after several hours in culture, and these cells were selected for ICSI. When no movement was detected, sperm were chosen for ICSI on the basis of morphologic criteria, as the success of this approach has been previously documented (Prins et al, 1999). Fresh sperm was obtained through either TESE or MESA, as described above. Sperm cells were then washed with HTF culture medium supplemented with Plasmanate (plasma protein—Bayer Biological) 5% volume: volume, and cultured until needed for ICSI. Remaining specimen was frozen for future cycles. Mature oocytes were microinjected with surgically retrieved sperm according to the technique of Palermo et al (1992).

Embryos were transferred under ultrasound guidance using a Wallace transfer catheter (Cooper Surgical, Shelton, Conn) on days 3 or 5 of embryo development. Luteal phase support was provided with the administration of intramuscular progesterone.

Pregnancy was confirmed by rising serum hCG concentrations in consecutive assays, 48 hours apart approximately 12 days following embryo transfer. A clinical pregnancy was defined by the presence of a gestational sac identified by ultrasound at 7 weeks.


   Results
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 Abstract
 Materials and Methods
 Results
Discussion
 References
 
IVF/ICSI cycles using cryopreserved and fresh sperm were performed in 183 and 36 women, respectively. Cryopreserved sperm was obtained through TESE for 173 women, while epididymal frozen sperm was used for the other 10. Fresh sperm was of testicular and epididymal origin in 33 and 3 patients, respectively. An average of 14.1 oocytes were retrieved in the fresh cycles (13.9 in cycles using testicular sperm and 17.0 in those done with epididymal sperm). For the cycles using cryopreserved sperm, an average of 12.6 oocytes were retrieved (12.6 in cycles using testicular sperm and 14.4 in those done with epididymal sperm). Table 2 summarizes the data concerning the ICSI cycles using either fresh or cryopreserved sperm.

The fertilization rate for the entire dataset, including IVF/ICSI cycles using sperm obtained by MESA and TESE, was 59.9% for cryopreserved sperm and 53.6% when fresh sperm was used ({chi}2 P-{alpha} < .02, Cramer's {phi} 0.04). For treatment cycles using TESE sperm, the fertilization rate was 60.0% for cryopreserved sperm and 55.1% for fresh sperm. Chi-square P-{alpha} was computed to be .075, greater than the chosen threshold value of 0.05. Thus, although the fertilization rate was higher in the cryopreserved group, at this point, the difference cannot be considered significant. Cohen effect size was computed at 0.03, yielding for P-ß = 0.8, 6597 ova would be required to demonstrate similarity between fresh and cryopreserved sperm in the TESE group. If the null hypothesis were to be rejected, 7524 ova would be necessary to demonstrate superiority of cryopreserved sperm in this group at a P-{alpha} significance level of .05.

The pregnancy rate for the TESE group was 27.3% using cryopreserved sperm and 27% for fresh sperm. These outcomes were statistically similar, with power calculated to be 0.971 (the effect size was calculated at 0.002).


   Discussion
Top
 Abstract
 Materials and Methods
 Results
 Discussion
References
 
Traditionally, the success of IVF was considered to rely on motile sperm in large numbers. This concept has been subject to change since the introduction of ICSI, requiring only a single sperm for successful fertilization and pregnancy. In fact, sperm is immobilized before its intracytoplasmic injection. Currently, only little data links sperm morphology to fertilizing capability in ICSI. In the absence of an accurate method to assess the fertilizing potential of a viable sperm, arbitrary characteristics are used to select sperm for ICSI. As ICSI bypasses sperm-transportation issues, its success would depend on the rapidity and efficacy of DNA release and integration. Under these circumstances, usage of cryopreserved sperm may not be disadvantageous.

Variable outcomes of ICSI using cryopreserved sperm have been reported (Table 1). Gil-Salom et al (1996) reported using surgically retrieved testicular sperm for ICSI with a 53% fertilization rate using fresh sperm and a 55% fertilization rate with cryopreserved sperm. No pregnancies were achieved in the group using fresh sperm, and 6 pregnancies using frozen sperm were noted (33% pregnancy rate). Similar fertilization and clinical pregnancy rates for fresh and cryopreserved sperm (47% fresh, 44% frozen and 26% fresh, 27% frozen, respectively) were also reported by Friedler et al (1997), after using testicular sperm for ICSI cycles in 18 men with NOA. Prins et al (1999) investigated the results of ICSI using cryopreserved sperm obtained from both obstructive and NOA men. The fertilization rate for cryopreserved testicular sperm in ICSI was 58% from an obstructed testis and 60% for NOA, and the clinical pregnancy rates per ICSI cycle for obstructive and nonobstructive etiologies were 43% and 67%, respectively. Favorable results for cryopreserved sperm were also demonstrated in a small series, in which ICSI outcomes of fresh and frozen testicular sperm were directly compared (Habermann et al, 2000). In that study, Habermann et al reported a 56% fertilization rate with fresh and a 61% rate with frozen testicular sperm. Clinical pregnancy rates per cycle were 33% with fresh and 41% with frozen testicular sperm. Verheyen et al (2004) have demonstrated comparable fertilization, implantation, and ongoing pregnancy rates in IVF/ICSI cycles using either cryopreserved or fresh surgically retrieved sperm obtained from men with NOA. While a higher embryo transfer rate was observed in fresh cycles, the authors concluded that diagnostic testicular biopsy followed by sperm cryopreservation could be the procedure of choice for patients with testicular failure.

The conclusions reached by these authors regarding the equivalent efficacy of fresh and cryopreserved sperm for IVF/ICSI are not shared by all reproductive centers. This discrepancy of opinions may be attributed to the reluctance of some centers to use cryopreserved and thawed testicular sperm. This reluctance may be due to lack of expertise in the technique of isolation of spermatozoa from testicular tissue or in the technique of freezing testicular sperm. Indeed, other investigators have found that ICSI outcomes using cryopreserved sperm were not comparable with a fresh specimen (Romero et al, 1996; Verheyen et al, 1997). A recent meta-analysis of published IVF/ICSI data demonstrated no difference between cycles using fresh or frozen-thawed sperm in terms of fertilization and ongoing pregnancy rates, but a significantly higher implantation rate and an increase in the clinical pregnancy rate of borderline statistical significance using fresh sperm (Nicopoullos et al, 2004a). When fresh and frozen-thawed epididymal sperm were compared separately, there were no significant differences in the fertilization, implantation, and ongoing pregnancy rates, but the clinical pregnancy rate was significantly higher with fresh sperm. No difference in fertilization or pregnancy outcome was noted when the testicular cycles were analyzed separately, but the implantation rate was significantly impaired using frozen-thawed sperm.

The use of cryopreserved sperm for ICSI offers several advantages. First, it may decrease the number of surgical interventions, possibly to 1 testicular biopsy, as sperm retrieved could be banked for future assisted reproductive treatments. Second, obtaining cryopreserved testicular sperm before ICSI could obviate the possibility of encountering a patient in whom no testicular sperm is found on the day of his partner's IVF procedure (Oates et al, 1997). Furthermore, the couple would not require simultaneous procedures, which can create substantial inconvenience.

In our present study, we embarked on an analysis of a large series, allowing for stringent statistical results. While ICSI fertilization rates were found to be similar for fresh and cryopreserved testicular sperm (55% in 387 oocytes with fresh testicular sperm, and 60% in 2714 oocytes with frozen testicular sperm), 7524 ova would be required to prove the superiority of frozen sperm at 0.8 power (P-{alpha} = 0.05). We expect to obtain that data some time after the year 2010. Given that the fertilization rates are persistently close in our series (and in fact, frozen rates consistently exceed fresh ones), we are comfortable with the use of cryopreserved testicular sperm in ICSI.

It may be speculated that the trend toward a higher fertilization rate observed with cryopreserved sperm in our study is related to the effect of the freeze-thaw cycle on the spermatozoal cell membrane. Rupture of the cell membrane due to osmotic stress and ice-crystal formation, the chief damaging event for freeze-thaw of sperm, could possibly facilitate release, dissolution, and integration of DNA once the sperm is injected into the ova's cytoplasm, leading to a higher fertilization rate.

Interestingly in this large series, clinical pregnancy rates were 27.0% for fresh and 27.3% for frozen testicular sperm, equivalent at a power of 0.97. Others in recent larger series noted similar pregnancy rates with fresh and frozen testicular sperm, with small differences in fertilization rates (Ben Rhouma et al, 2003; Schwarzer et al, 2003a,b; Nicopoullos et al, 2004b). While sperm from men with NOA may fare more poorly than those with obstructive azoospermia, outcomes of fresh and frozen sperm were similar within each etiologic group (Schwarzer et al, 2003b).

In summary, our findings indicate comparable ICSI outcomes for cryopreserved and fresh sperm, regardless of etiology.


   References
Top
 Abstract
 Materials and Methods
 Results
 Discussion
 References
 
Ben Rhouma K, Marrakchi H, Khouja H, Attalah K, Ben Miled E, Sakly M. Outcome of intracytoplasmic injection of fresh and frozen-thawed testicular spermatozoa. A comparative study. J Reprod Med. 2003; 48: 349 -354.[Medline]

Cohen J. Statistical Power Analysis for the Behavioral Sciences. 2nd ed. Hillsdale, NJ: Lawrence Erlbaum Associates Inc; 1988 .

Devroey P, Liu J, Nagy Z, Goossens A, Tournaye H, Camus M, Van Steirtghem A, Silber S. Pregnancies after testicular sperm extraction and intracytoplasmic sperm injection in non-obstructive azoospermia. Hum Reprod. 1995; 10: 1457 -1460.[Medline]

Friedler S, Raziel A, Soffer Y, Strassburger D, Komarovsky D, Ron-El R. Intracytoplasmic injection of fresh and cryopreserved testicular spermatozoa in patients with nonobstructive azoospermia—a comparative study. Fertil Steril. 1997; 68: 892 -897.[CrossRef][Medline]

Gil-Salom M, Romero J, Minguez Y, Rubio C, De los Santos MJ, Remohi J, Pellicer A. Pregnancies after intracytoplasmic sperm injection with cryopreserved testicular spermatozoa. Hum Reprod. 1996; 11: 1309 -1313.[Abstract/Free Full Text]

Habermann H, Seo R, Cieslak J, Niederberger C, Prins GS, Ross L. In vitro fertilization outcomes after intracytoplasmic sperm injection with fresh or frozen-thawed testicular spermatozoa. Fertil Steril. 2000;73: 955 -960.[CrossRef][Medline]

Manning M, Junemann KP, Alken P. Decrease in testosterone blood concentrations after testicular sperm extraction for intracytoplasmic sperm injection in azoospermic men. Lancet. 1998; 352: 37 .[CrossRef][Medline]

Nicopoullos JDM, Gilling-Smith C, Almeida PA, Norman-Taylor J, Grace I, Ramsay JW. Use of surgical sperm retrieval in azoospermic men: a meta-analysis. Fertil Steril. 2004a; 82: 691 -701.[CrossRef][Medline]

Nicopoullos JDM, Gilling-Smith C, Almeida PA, Ramsay JW. The results of 154 ICSI cycles using surgically retrieved sperm from azoospermic men. Hum Reprod. 2004b; 19: 579 -585.[Abstract/Free Full Text]

Nudell DM, Conaghan J, Pedersen RA, Givens CR, Schriock ED, Turek PJ. The mini-micro-epididymal sperm aspiration for sperm retrieval: a study of urological outcomes. Hum Reprod. 1998; 13: 1260 -1265.[Abstract/Free Full Text]

Oates RD, Mulhall J, Burgess C, Cunningham D, Carson R. Fertilization and pregnancy using intentionally cryopreserved testicular tissue as the sperm source for intracytoplasmic sperm injection in 10 men with non-obstructive azoospermia. Hum Reprod. 1997; 12: 734 -739.[Abstract/Free Full Text]

Palermo GD, Joris H, Devroey P, Van Steirteghem AC. Pregnancies after intracytoplasmic injection of single spermatozoon into an oocyte. Lancet. 1992;340: 17 -18.[CrossRef][Medline]

Palermo GD, Schlegel PN, Hariprashad JJ, Ergun B, Mielnik A, Zaninovic N, Veeck LL, Rosenwaks Z. Fertilization and pregnancy outcome with intracytoplasmic sperm injection for azoospermic men. Hum Reprod. 1999;14: 741 -748.[Abstract/Free Full Text]

Prins GS, Dolgina R, Studney P, Kaplan B, Ross L, Niederberger C. Quality of cryopreserved testicular sperm in patients with obstructive and nonobstructive azoospermia. J Urol. 1999; 161: 1504 -1508.[CrossRef][Medline]

Romero J, Remohi J, Minguez Y, Rubio C, Pellicer A, Gil-Salom M. Fertilization after intracytoplasmic sperm injection with cryopreserved testicular spermatozoa. Fertil Steril. 1996; 65: 877 -879.[Medline]

Schlegel PN. Testicular sperm extraction: microdissection improves sperm yield with minimal tissue excision. Hum Reprod. 1999; 14: 131 -135.[Abstract/Free Full Text]

Schlegel PN, Berkeley AS, Goldstein M, Cohen J, Alikani M, Adler A, Gilbert BR, Rosenwaks Z. Epididymal micropuncture with in vitro fertilization and oocyte micromanipulation for the treatment of unreconstructable obstructive azoospermia. Fertil Steril. 1994; 61: 895 -901.[Medline]

Schlegel PN, Palermo GD, Goldstein M, Menendez S, Zaninovic N, Veeck LL, Rosenwaks Z. Testicular sperm extraction with intracytoplasmic sperm injection for nonobstructive azoospermia. Urology. 1997; 49: 435 -440.[CrossRef][Medline]

Schwarzer JU, Fiedler K, Hertwig IV, Krusmann G, Wurfel W, Muhlen B, Pickl U, Lochner-Ernst D, Schleyer M, Ovens-Rader A, Hennig M. Male factors determining the outcome of intracytoplasmic sperm injection with epididymal and testicular spermatozoa. Andrologia. 2003a; 35: 220 -226.[CrossRef][Medline]

Schwarzer JU, Fiedler K, Hertwig IV, Krusmann G, Wurfel W, Schleyer M, Muhlen B, Pickl U, Lochner-Ernst D. Sperm retrieval procedures and intracytoplasmatic spermatozoa injection with epididymal and testicular sperms. Urol Int. 2003b; 70: 119 -123.[CrossRef][Medline]

Silber SJ, Van Steirteghem AC, Liu J, Nagy Z, Tournaye H, Devroey P. High fertilization and pregnancy rate after intracytoplasmic sperm injection with spermatozoa obtained from testicle biopsy. Hum Reprod. 1995;10: 148 -152.[Abstract/Free Full Text]

Silber SJ, Van Steirteghem AC, Nagy Z, Liu J, Tournaye H, Devroey P. Normal pregnancies resulting from testicular sperm extraction and intracytoplasmic sperm injection for azoospermia due to maturation arrest. Fertil Steril. 1996; 66: 110 -117.[Medline]

Turek PJ, Ljung BM, Cha I, Conaghan J. Diagnostic findings from testis fine needle aspiration mapping in obstructed and nonobstructed azoospermic men. J Urol. 2000; 163: 1709 -1716.[CrossRef][Medline]

Verheyen G, Nagy Z, Joris H, De Croo I, Tournaye H, Van Steirteghem A. Quality of frozen-thawed testicular sperm and its preclinical use for intracytoplasmic sperm injection into in vitro-matured germinal-vesicle stage oocytes. Fertil Steril. 1997; 67: 74 -80.[CrossRef][Medline]

Verheyen G, Vernaeve V, Van Landuyt L, Tournaye H, Devroey P, Van Steirteghem A. Should diagnostic testicular sperm retrieval followed by cryopreservation for later ICSI be the procedure of choice for all patients with non-obstructive azoospermia? Hum Reprod. 2004; 19: 2822 -2830.[Abstract/Free Full Text]





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