Controlled comparison of conventional in-vitro fertilization and intracytoplasmic sperm injection in patients with asthenozoospermia

G. Verheyen1, H. Tournaye, C. Staessen, A. De Vos, M. Vandervorst and A. Van Steirteghem

Centre for Reproductive Medicine, Academic Hospital, Dutch-speaking Brussels Free University, Laarbeeklaan 101, B-1090 Brussels, Belgium


    Abstract
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
A controlled comparison between conventional in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) has been carried out for patients with <=5% rapid progressive (type A) spermatozoa in their fresh semen. Twenty couples were allocated to the study. All semen samples fulfilled the minimum criteria to be allocated to the conventional IVF programme. The two pronuclear (2PN) fertilization rate per retrieved cumulus–oocyte complex was significantly higher after ICSI (63.4%) than after conventional IVF (22.9%), with complete fertilization failure after IVF in 10 out of the 20 cycles. Embryo quality was similar for both treatments. Sixteen patients received only ICSI embryos, two patients only IVF embryos and two patients received IVF and ICSI embryos. The ongoing clinical pregnancy rate was 45%, the implantation rate was 37%. Comparison of the characteristics of patients/cycles with and without 2PN fertilization revealed a higher proportion of progressively motile spermatozoa in the prepared sperm fraction for the group of patients with fertilization after conventional IVF. It can be concluded from this study that absence of or an extremely low proportion of rapid progressive motility in fresh semen indicates a high risk of complete fertilization failure with conventional IVF.

Key words: asthenozoospermia/controlled study/fertilization failure/IVF versus ICSI/motility


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Since its introduction in 1992 (Palermo et al., 1992Go), intracytoplasmic sperm injection (ICSI) has been applied worldwide as an efficient technique for the treatment of severe male-factor infertility cases who are ineligible for conventional in-vitro fertilization (IVF). The global results in terms of fertilization rates and pregnancy rates have even appeared to be unrelated to the quality of the basic sperm parameters (Mansour et al., 1995Go; Nagy et al., 1995Go; Svalander et al., 1996Go). A few prospective, controlled studies have compared the efficacy of ICSI and conventional IVF on sibling oocytes for different male indications. In some studies (Aboulghar et al., 1995Go, 1996Go; Calderon et al., 1995Go), the results were highly supportive of the ICSI procedure. Conventional IVF was associated with almost 50% of total fertilization failures in the latter study. Other groups compared IVF and ICSI in cases of severe teratozoospermia. According to some authors, the problem of a high proportion of abnormal forms can be overcome by `high insemination concentration (HIC)' for conventional IVF (Ord et al., 1993Go; Hall et al., 1995Go; Oehninger et al., 1996Go). Others, however, recommend ICSI or a diagnostic IVF versus ICSI treatment for severe teratozoospermia (Payne et al., 1994Go; Fishel et al., 1995Go). It may be assumed that the difference in efficiency between IVF and ICSI for andrological reasons depends on the inclusion criteria for IVF, on the performance of the IVF and ICSI programme, and on the number and quality of the inseminated spermatozoa in IVF. Comparison of conventional IVF and ICSI is valid and can be carried out properly only when the sperm criteria that allow acceptance of a couple for IVF treatment are fulfilled.

It is clear that the severe male indications can be treated successfully only with ICSI. It is less clear whether a difference in efficiency between IVF and ICSI exists for the real borderline male cases that theoretically fulfil the criteria for conventional IVF. While teratozoospermia has been widely studied, the impact of borderline asthenozoospermia on fertilization and embryo quality after conventional IVF and ICSI is less clear. In most centres, a cut-off value for progressively motile spermatozoa after preparation is defined to determine the admittance of a couple to the conventional IVF programme. A minimum total number of rapid (type A, >25 µm/s) and slow (type B, 5–25 µm/s) progressively motile spermatozoa together is generally used (WHO, 1992); in our centre this number is >= 500 000 type A+B spermatozoa. The question arises as to whether the predominant presence of slow progressive type B spermatozoa in semen may be an indication for ICSI, or a contra-indication for conventional IVF.

The aim of the present prospective, controlled study was therefore to compare the efficiency of conventional IVF and ICSI in cases of asthenozoospermia, defined in this study as <=5% type A motility in the fresh semen sample.


    Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Patient selection
Most couples were allocated to the study during their visit to the outpatient clinic, based on the quality of the diagnostic semen examination. Semen characteristics fulfilled the following inclusion criteria: (i) <=5% rapid progressive type A motility (WHO, 1992) in the fresh semen; (ii) >=500 000 progressively motile spermatozoa (type A+B) after preparation of the entire semen sample, which is the limit for sperm quality required for admission to the conventional IVF programme in our centre. Other semen parameters were not taken into consideration. On the day of oocyte retrieval, couples were effectively included in the study only when their semen fulfilled the above criteria again. Five couples planned at the outpatient clinic were excluded from the study for this reason. Fourteen patients were accepted who revealed severe asthenozoospermia (<=5% rapid progressive motility) on both occasions while another six patients were allocated to the study on the day of oocyte retrieval on the basis of their sperm quality at that moment. If less than eight cumulus–oocyte complexes were retrieved at ovum retrieval (third inclusion criterion), all oocytes were treated by ICSI, and these patients also were excluded from the study.

In total, 20 cycles (20 couples) were carried out. The mean patient age was 31.6 ± 3.4 years (range 25–39) for the female partners and 35.4 ± 4.9 years (range 27–45) for the male partners.

Ovarian stimulation
Female partners underwent ovarian stimulation using a gonadotrophin-releasing hormone analogue suppression protocol with buserelin (Suprefact nasal spray; Hoechst, Frankfurt, Germany) combined with human menopausal gonadotrophins (HMG). Oocyte-cumulus complexes were recovered by vaginal ultrasound-guided retrieval 36 h after administration of 10 000 IU of human chorionic gonadotrophin (HCG).

Semen evaluation and preparation
Fresh semen samples were provided by masturbation on the day of oocyte collection. After liquefaction, sperm concentration and motility were assessed according to the recommendations of the World Health Organization (1992). Sperm morphology was evaluated using the strict Kruger criteria (Kruger et al., 1986Go). Semen samples from all patients included in the study showed <=5% rapid progressive motility. All semen samples were prepared by discontinuous density gradient centrifugation, initially based on Percoll (95%–47.5%, Pharmacia, Uppsala, Sweden), but later replaced by Pure Sperm (90%–45%, Nidacon Laboratories, Göteborg, Sweden). A 1 ml fraction of fresh semen was placed on a gradient consisting of 1 ml of the bottom fraction and 1 ml of the top fraction. Multiple gradients were made whenever necessary. After centrifugation at 300 g for 20 min, 200–400 µl of the bottom fraction were aspirated and washed twice before evaluation. After concentration and motility had been assessed, this fraction was either diluted or concentrated depending on the number of progressively motile (type A+B) spermatozoa per microlitre.

Oocyte retrieval and preparation
Oocyte retrieval was carried out by ultrasound-guided transvaginal puncture of the follicles 36 h after 10 000 IU HCG administration. The first cumulus–oocyte complex was allocated either to ICSI or to conventional IVF according to a randomization table. The subsequent cumulus–oocyte complexes were further alternately allocated to ICSI or IVF; those used for IVF were individually cultured in 25 µl droplets of B2 medium under paraffin oil.

In conventional IVF, oocytes were inseminated with 5000 progressively motile spermatozoa (type A+B) at least 2 h after ovum retrieval. The volume to be added ranged between 1 and 5 µl. If after concentrating the final sperm fraction the calculated volume providing 5000 motile cells exceeded 5 µl, the excess medium was first removed from the microdroplet before the sperm volume was added. The cumulus–oocyte complexes allocated to ICSI were enzymatically denuded from their cumulus cells by exposure to a solution of 10 IU/ml hyaluronidase (Type VIII, Sigma Chemical Company, St Louis, MO, USA) followed by pipetting. Only the mature, metaphase-II oocytes were injected. Care was taken to perform the insemination of the IVF oocytes and the injection of the ICSI oocytes at the same hour of the day (around 14:00). The ICSI procedure was carried out as previously described (Van Steirteghem et al., 1995Go).

Fertilization, embryo quality and embryo transfer
Assessment of fertilization was carried out about 18 h after oocyte insemination and injection. Oocytes with two distinct pronuclei (2PN) together with two distinct or fragmented polar bodies were considered normally fertilized. For ICSI oocytes, the pronuclei had sometimes disappeared by that time, and these oocytes were considered normally fertilized when two polar bodies and normal cleavage were observed. Normal fertilization rate was always calculated as the number 2PN over the number of cumulus–oocyte complexes, independent of the nuclear maturity, as well for IVF as for ICSI. At 42–44 h post-insemination and post-injection, the morphological quality and developmental speed of the embryos were assessed. Embryos were classified into different categories according to the proportion of fragments: type A embryos without fragments, type B embryos with fragmentation up to 20%, type C embryos with fragmentation >=20% and <50%, and type D embryos with >=50% fragmentation. For each category, the percentage of embryos derived from 2PN fertilized oocytes was calculated. The normal cleaving embryos (type A, B and C) were also classified according to their speed of development, as 2-cell, 3- or 4-cell or 5–8 cell embryos. Embryos up to type C (<50% fragmentation) were replaced into the uterine cavity about 48 h after insemination or ICSI. Supernumerary good-quality embryos (type A or type B only) were frozen at day 2 or day 3.

The embryo transfer policy was the following: always the best-quality embryos were replaced, two (elective embryo transfer) or three depending on their morphological quality (Staessen et al., 1993Go), and preferably derived from the same treatment procedure (conventional IVF or ICSI). Where a similar high quality of the embryos allowed a choice between IVF and ICSI embryos, preference was given to the IVF embryos as the aim was to continue the treatment by the least complicated and the least expensive procedure (IVF), if pregnancy failed to occur. A rise in serum HCG on two consecutive occasions from day 11 onwards after embryo transfer indicated pregnancy. A clinical pregnancy was defined by the presence of a gestational sac at ultrasonography after approximately 7 weeks of pregnancy. Implantation rate was defined as the total number of fetal heart beats per total number of embryos replaced.

Parameters for evaluation
The following parameters were used to compare the efficiency of conventional IVF and ICSI: percentage 2PN fertilization, percentage 1 PN and >=3 PN, morphological quality and rate of development of the embryos at 42–44 h post-insemination and post-injection, number of embryos transferred on day 2, number of embryos frozen (on day 2 or 3) and total number of embryos transferred or frozen. The fertilization rate was always calculated as the number of 2PN oocytes compared to the number of retrieved cumulus–oocyte complexes. As the origin of the embryos for transfer was not randomized, no conclusion could be drawn regarding the pregnancies.

Statistical analysis
The Wilcoxon signed-rank test for paired data was used to compare the above parameters on sibling oocytes. The Mann–Whitney U test was used to compare results between the group of patients with fertilization after conventional IVF and the group of patients without fertilization after conventional IVF. All tests were performed at the 5% level of significance.


    Results
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Semen parameters
All patients observed 3–5 days sexual abstinence before preparing their semen samples. In terms of macroscopic aspects, all semen samples showed normal liquefaction, but five out of the 20 showed a slightly to moderately abnormal viscosity. The results of the basic sperm parameters of the fresh diagnostic semen samples (from outpatient clinic) and the fresh therapeutic semen samples (oocyte retrieval, ovum retrieval) are presented in Table IGo. The concentration of spermatozoa revealed a wide range on both occasions. The same observation was made for the total sperm count, after taking the semen volume into account. The mean percentage type A motility was higher in the preliminary semen samples, due to six patients who were allocated to the study only on the day of ovum retrieval as they had >5% type A motility (range 8–38) in their preliminary semen samples. At oocyte retrieval, however, all patients showed a maximum of 5% type A motility. The total percentage of progressively motile cells (type A+B) was similar on both occasions. Mean percentages of normal morphology at the outpatient clinic and oocyte retrieval were comparable, with respectively 10 and 8 cases showing <5% normal forms.


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Table I. Characteristics of the diagnostic (D, from outpatient clinic) and the therapeutic (T, at ovum retrieval) fresh semen samples from 20 patients
 
Tests for antisperm antibodies IgG and IgA were carried out only for the diagnostic semen samples. IgG antibodies were absent in 18/20 patients, while two had 100% of their spermatozoa bound with IgG antibodies. Only one patient had IgA antibodies (96%). Two patients had 1–1.5x106/ml peroxidase-positive round cells (white blood cells).

Fertilization and embryo quality
The mean number of cumulus–oocyte complexes per patient was 14.7, a mean of 7.4 oocytes to be treated by IVF and 7.3 oocytes to be treated by ICSI. Although only the mature, metaphase II oocytes were injected, percentages of 2PN, 1PN and >=3PN per cycle have always been calculated as a proportion of the number of retrieved cumulus–oocyte complexes (Table IIGo). This is considered to be the only way to carry out a valid comparison, as oocyte maturity on the day of oocyte retrieval is checked only for the ICSI oocytes and not for IVF oocytes. The fertilization rate after IVF (a mean of 22.9% per cycle) was far below the fertilization rate after ICSI (63.4%, P < 0.001). Most striking was the observation of complete fertilization failure by conventional IVF in 10 out of the 20 cycles (50%), while 2PN fertilization always ensued after ICSI. Patients with fertilization after IVF (n = 10) showed a reasonable fertilization rate of 45.7% after IVF, which was not significantly different from the 59.4% obtained after ICSI for the same 10 patients. Percentages of 1PN and >=3 PN were similar for both treatment procedures.


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Table II. Fertilization rates after IVF and ICSI (20 cycles)
 
Comparison of the quality of embryos derived from IVF or ICSI was based on only nine cycles, as no fertilization had been observed after IVF in 10 cases, and another patient had only one fertilized oocyte after IVF, which did not cleave. In terms of morphological quality, embryos were divided into four categories. Percentage total cleavage was the number of transferable embryos (up to type C) as a proportion of the number of fertilized oocytes (Table IIIGo). Calculated on a patient basis, the percentage of embryos per morphology class was not significantly different between conventional IVF and ICSI. Considering the developmental speed, ICSI embryos were further developed than IVF embryos at 42–44 h post-insemination and post-injection. The proportion of embryos at the 2-cell stage was significantly higher for IVF than for ICSI on the morning of the embryo transfer (P < 0.05).


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Table III. Embryo quality at 42–44 h after conventional IVF and ICSI (9 cycles)
 
Embryo transfer, pregnancy rate, and implantation rate
As the best-quality embryos were always replaced, derived from IVF, from ICSI, or from both treatments, no assessment of the relationship between the treatment procedure and implantation can be made. All 20 patients had at least one embryo replaced. Most patients (n = 16) received only ICSI embryos (2.1 per patient) for two reasons: no IVF embryos were available in 10 cycles, and ICSI embryos often showed a more advanced developmental stage at the moment of embryo transfer. Two patients received only IVF embryos (2.0 per patient) and two patients were given a transfer of IVF and ICSI embryos together (2.5 per patient). Consequently, significant differences between IVF and ICSI ensued in terms of the total number of embryos replaced (P < 0.001) and in terms of the total number of embryos replaced and frozen (P = 0.001, Table IVGo). Eleven patients (55%) showed a positive HCG, one had a biochemical pregnancy, and another pregnancy resulted in an early miscarriage. Of the nine patients with an ongoing clinical pregnancy (45% per embryo transfer), seven received only ICSI embryos. The implantation rate was 37%, the ongoing implantation rate beyond 20 weeks of gestation was 30%.


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Table IV. Embryo transfer, pregnancy rate and implantation rate (20 cycles)
 
Comparison of cycles with (fert+) and without (fert–) fertilization after IVF
In 10 cycles, no fertilization ensued for the oocytes treated by conventional IVF. The characteristics of the patients and/or cycles with (fert+, n = 10) and without (fert–, n = 10) fertilization after IVF were therefore compared (Table VGo). For most of the parameters, no difference was observed between the patient populations with and without fertilization after conventional IVF. Although sperm concentration had a tendency to be higher in the fert+ group, this was due rather to the inclusion of a few cases with concentrations >100x106/ml. The difference became more pronounced and significant when the total sperm count on the day of oocyte retrieval (sperm concentrationxvolume) was considered (P = 0.05, Table VGo). Percentage progressive motility (type A or type A+B) and percentage normal morphology in the fresh semen was comparable for groups fert+ and fert–. The total number of progressively motile cells, however, was higher in the fert+ group than in the fert– group (P = 0.05, Table VGo). Five out of 10 patients in fert+ and three out of 10 in fert– groups showed severe teratozoospermia (<=5% normal morphology) in combination with their low proportion of type A motility.


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Table V. Comparison of characteristics of patients and cycles with (fert+) or without (fert–) fertilization after conventional IVF
 
The quality of the final sperm fraction, after preparation by density gradient centrifugation, may be judged by the proportion of progressively motile spermatozoa (purity of motility) and occasionally by the volume of the fraction to be used for insemination. In our microdroplet system, a maximum volume of 5 µl sperm fraction was added to each droplet (25 µl) in order to avoid further dilution within the droplet. In this way, the concentration of the final sperm fraction was adapted so as to obtain 5000 progressively motile spermatozoa within a volume ranging from 1 to 5 µl. If more than 5 µl was required from the maximally concentrated final fraction in order to obtain enough spermatozoa, the excess volume was first removed from the microdroplet of medium containing the oocyte, before the appropriate sperm volume was added. This, in general, happens rather seldom but in this study it occurred in five out of 10 cases (mean of 6.3 µl inseminated for the 10 patients in the fert– group) from the fert– group and in two out of 10 cases (mean of 3.5 µl inseminated for the 10 patients in the fert+ group) from the fert+ group. Furthermore, the fert+ population showed a significantly higher proportion of progressive motility in the final sperm fraction than did the fert– population (P < 0.01, Table VGo), with five cases in the fert+ group showing predominantly slow type B motility in the final fraction, as against eight out of the 10 cases in the fert– group.

No difference between the two subpopulations was observed in the 2PN rate obtained after ICSI. The pregnancy rate was higher in the fert+ group, where the higher number of embryos available allowed a greater selection of the embryos for transfer.


    Discussion
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 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
The choice of the most appropriate assisted-reproduction treatment (IUI, IVF, or ICSI) for the individual couple is often based on the semen quality of the male partner. ICSI is highly efficient in cases of severe male infertility who would otherwise be untreatable with their own gametes. The success of ICSI, however, has undoubtedly led to an overuse of this more invasive procedure. An obvious reason for this is certainly the avoidance of complete fertilization failures. The risk of failure of fertilization after conventional IVF with normozoospermic semen has indeed been a frustrating element since the introduction of IVF. Unexplained lack of fertilization after IVF is observed in about 8% of the cycles. According to some studies, this feature shows a low recurrence rate (Molley et al., 1991Go; Ben-Shlomo et al., 1992Go; Lipitz et al., 1993Go, 1994Go). According to other reports, total failure of fertilization after IVF as well as very low fertilization rates are repetitive phenomena indicating a possible underlying, undiagnosed sperm or oocyte pathology (Calderon et al., 1995Go; Roest et al., 1998Go). After ICSI, fertilization failures rarely occur (2.8%), and are repetitive in only 15% of cases (Liu et al., 1995Go; Vandervorst et al., 1997Go; Flaherty et al., 1998Go). A treatment combining IVF and ICSI on sibling oocytes has therefore been advised in the literature in order to avoid or reduce the proportion of failed fertilization cycles. Several studies have compared conventional IVF and ICSI for unexplained or tubal infertility with conflicting results: Yang et al. (1996) reported similar fertilization rates without failures for a small series of cycles (n =13), while others found similar fertilization rates but 22% and 11% fertilization failures after IVF in larger series of cycles (respectively n = 22 by Aboulghar et al., 1996Go and n = 70 by Ruiz et al., 1997Go).

Differences between IVF and ICSI are more pronounced in cases of male subfertility. For patients with borderline semen, ICSI has shown a better performance than conventional IVF in terms of fertilization rate and absence of fertilization failure (Aboulghar et al., 1995Go, 1996Go; Calderon et al., 1995Go). Aboulghar et al. reported a fertilization failure rate of 50% after IVF, which is very high with regard to the reported reasonable semen quality (Aboulghar et al., 1995Go). Calderon and colleagues included a few patients with single, double, or triple sperm defects who should in fact be considered untreatable by conventional IVF (Calderon et al., 1995Go). In each of his three defined categories of sperm defects, at least one patient had no progressively motile spermatozoa, which is a clear contra-indication for conventional IVF. Such remarks stress the variability in the interpretation of `borderline semen' quality between groups and argue for a critical analysis of the reported data. As regards teratozoospermia, a high risk of fertilization failure (11/18 patients) after IVF leading to extreme differences in fertilization rates between IVF and ICSI (76% for ICSI against 15% for IVF) has been reported (Payne et al., 1994Go). This problem seems partly to be solved by the procedure of `high insemination concentration' for IVF (Ord et al., 1993Go; Hall et al. 1995Go), but remains in cases of severe teratozoospermia (<5% normal morphology) (Fishel et al., 1995Go).

For asthenozoospermia, a controlled comparison of conventional IVF and ICSI has not yet been reported. In the present study, asthenozoospermia is defined as a very low proportion of rapid progressively (type A) motile spermatozoa of <=5% in the fresh semen sample. Different conditions may impair sperm motility, but the aetiology of asthenozoospermia often remains unknown. Anti-sperm antibodies, infection of the genital tract, prolonged periods of anejaculation, high semen viscosity, ultrastructural defects and metabolic defects are the commonest causes (Vandervorst et al., 1997Go). Some patients in this study had a high semen viscosity (5/20), and/or antisperm antibodies (2/20), and/or slightly elevated leukocyte counts (2/20). Although these parameters may impair motility or interfere with fertilization results after conventional IVF, the patients showing these defects were equally distributed over the fert– and the fert+ groups (Table VGo).

The most striking observation in the comparison between IVF and ICSI in this study population is the extremely low fertilization rate and high fertilization failure rate after conventional IVF. Once 2PN fertilization with conventional IVF had taken place, however, the rate was reasonably high (45.7%) but showed the tendency to be lower than the 2PN rate after ICSI (59.4%) for the same 10 patients. The observation that the 2PN rate after ICSI was 67.5% and 59.4% for the fert– and the fert+ groups respectively, indicates that penetration through the oocyte investments after conventional IVF, rather than post-penetration events, are impaired in this study population. Differences in developmental speed (Table IIIGo) of the IVF and ICSI embryos are inherent to the ICSI technique itself. Nagy et al. (1998) showed that pronucleus formation after ICSI occurs 4 h sooner than after IVF due to the bypassing of several mechanical barriers. That is the reason why more IVF embryos than ICSI embryos were still at the 2-cell stage on the morning of day 2. In the present study, more ICSI embryos were replaced (36/43), even in the population that also achieved fertilization after IVF (fert+), which is mainly due to the later cleavage stage of the ICSI embryos at the time of embryo transfer, rather than to a difference in morphological quality. A high pregnancy rate was obtained. Four pregnancies, obtained in the patient population without fertilization after IVF, would not have occurred if ICSI had not been used. At least for these patients, the cycle was rescued by the application of combined ICSI and conventional IVF.

As half of the patients obtained fertilization only with ICSI and the other half with both ICSI and IVF, the two subpopulations were carefully explored. Semen samples with high viscosity, high antisperm antibody titres or leukocytes seemed equally distributed over the two subpopulations. Although each of these defects may interfere with fertilization after IVF, five out of 10 patients with fertilization after IVF had one of the three former defects, as well as five out of 10 patients with no fertilization after IVF. In terms of the basic sperm parameters, significant differences were observed for total sperm count and progressive motile sperm count on the day of oocyte retrieval. The progressively motile count ranged from 4.2x106 to 12.4x106 at oocyte retrieval for the fert– group, and from 5.0x106 to 83.0x106 in the fert+ group. More relevant seems the quality of the sperm fraction prepared for insemination and injection, which was better in terms of motility for patients who obtained fertilization with both treatment procedures (fert+). Olds-Clarke (1996) demonstrated that penetration of the cumulus oophorus and especially of the zona pellucida require a certain velocity (VCL) of the spermatozoa in order to generate high forces. However, penetration of the egg investments seems to be not only dependent on sperm velocity but also on the quality of the investments, which may vary from one woman to another. This aspect may partly explain why here fertilization occurs after IVF in certain patients and not in others.

Furthermore, patients with fertilization failure after conventional IVF (fert–) in the present study showed a high proportion of immotile spermatozoa (48%) in the inseminated sperm fraction, which was significantly different (P < 0.01) from that of the fert+ subpopulation (22%). In general, more than 80% progressive motility may be obtained after density gradient centrifugation. It is described in the literature, however, that high numbers of immotile and/or dead spermatozoa in the immediate vicinity of the oocyte may cause oxidative damage by the production of reactive oxygen species (Aitken and Clarkson, 1987Go; Aitken, 1994Go). Oxidative stress may lead to impaired fertilization and/or embryonic quality, especially after prolonged sperm-to-oocyte exposure (Aitken and Clarkson, 1987Go; Parinaud et al., 1993Go; Aitken, 1994Go; Gianaroli et al., 1998).

For several male patients in this study, asthenozoospermia (<5% type A motility) was not the sole sperm abnormality: it was often combined with teratozoospermia (<14% normal morphology). This additional defect may not be ignored as the fertilization rate after IVF is reported to be severely impaired in patients with less than 5% normal morphology (Kruger et al., 1988Go; Ombelet et al., 1994Go; Payne et al., 1994Go; Fishel et al., 1996). In the present study population, however, more semen samples from the fert+ group (6/10) showed severely defective sperm morphology (<5% normal forms) than did samples from the fert– group (3/10). The question, however, may be raised as to whether `high insemination concentration', which may rescue the IVF cycle in severe cases of male infertility according to several studies (Oehninger et al., 1988Go; Hammitt, 1993Go; Ord et al., 1993Go; Cowan et al., 1996Go), might be helpful in avoiding fertilization failures for patients with extremely low or absent type A motility.

From the present study, it may be concluded that a low rate of rapid progressive sperm motility (<5% type A) is associated with a high rate of complete fertilization failures after conventional IVF, while the fertilization rates after ICSI are within the expected range. Although most parameters were similar, the subpopulation without fertilization after IVF showed a lower total sperm count and lower progressive motile count in the fresh semen than the subpopulation with fertilization after IVF. Of paramount importance seems to be the quality of the inseminating sperm fraction, with a higher rate of immotile spermatozoa and predominantly slow progressive motility in patients without fertilization after IVF. As the differences between the two subgroups were not clear-cut, it still remains to detect the underlying factors which might have a prognostic value for the success of conventional IVF. So far, however, these data argue for the application of a diagnostic combined conventional IVF/ICSI treatment cycle for male subfertility characterized by low or no rapid progressive motility, in order to avoid complete fertilization failure with conventional IVF.


    Acknowledgments
 
The authors wish to thank the clinical, paramedical and laboratory staff of the Centre for Reproductive Medicine. Furthermore, we are grateful to Mr Frank Winter of the Language Education Centre of our university for correcting the manuscript. This work was supported by grants from the Fund for Scientific Research – Flanders.


    Notes
 
1 To whom correspondence should be addressed Back


    References
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Aboulghar, M.A., Mansour, R.T., Serour, G.I. and Amin, Y.M. (1995) The role of intracytoplasmic sperm injection (ICSI) in the treatment of patients with borderline semen. Hum. Reprod., 10, 2829–2830.[ISI][Medline]

Aboulghar, M.A., Mansour, R.T., Serour, G.I. et al. (1996) Intracytoplasmic sperm injection and conventional in vitro fertilization for sibling oocytes in cases of unexplained infertility and borderline semen. J. Assist. Reprod. Genet., 13, 38–42.[ISI][Medline]

Aitken, J.R. (1994) A free radical theory of male infertility. Reprod. Fertil. Dev., 6, 19–24.[ISI][Medline]

Aitken, J.R. and Clarkson, J.S. (1987) Cellular basis of defective sperm function and its association with the genesis of reactive oxygen species by human spermatozoa. J. Reprod. Fertil., 81, 459–469.[Abstract]

Ben-Shlomo, I., Bider, D., Dor, J. et al. (1992) Failure to fertilize in vitro in couples with male factor infertility: what next? Fertil. Steril., 58, 187–189.[ISI][Medline]

Calderon, G., Belil, I., Aran, B. et al. (1995) Intracytoplasmic sperm injection versus conventional in-vitro fertilization: first results. Hum. Reprod., 10, 2835–2839.[ISI][Medline]

Cowan, D.B., Santis, M., Keefe, T. et al. (1996) A bridge to intracytoplasmic sperm injection—high insemination concentrations benefit patients who have a reduced chance of fertilization with standard in-vitro fertilization. Hum. Reprod., 11, 1985–1989.[Abstract]

Fishel, S., Lisi, F., Rinaldi, L. et al. (1995) Intracytoplasmic sperm injection (ICSI) versus high insemination concentration (HIC) for human conception in vitro. Reprod. Fertil. Dev., 7, 169–175.[ISI][Medline]

Flaherty, S.P., Payne, D. and Matthews, C.D. (1998) Fertilization failures after ICSI. In Filicori, M. and Flamigni, C. (eds), Treatment of Infertility: The New Frontiers. Communications Media for Education Inc, New Jersey, USA, pp. 269–282.

Gianaroli, L., Magli, M.C., Ferraretti, A.P. et al. (1996) Reducing the time of sperm-oocyte interaction in human in-vitro fertilization improves the implantation rate. Hum. Reprod., 11, 166–171.[Abstract]

Hall, J., Fishel, S., Green, S. et al. (1995) Intracytoplasmic sperm injection versus high insemination concentration in-vitro fertilization in cases of severe teratozoospermia. Hum. Reprod., 10, 493–496.[ISI][Medline]

Hammitt, D. (1993) Treatment of male factor infertility by in vitro insemination with high concentrations of motile sperm. Semin. Reprod. Endocrinol, 11, 72–82.[ISI]

Kruger, T.F., Menkveld, R., Stander, F.S.H. et al. (1986) Sperm morphologic features as a prognostic factor in in vitro fertilization. Fertil. Steril., 46, 1118–1123.[ISI][Medline]

Kruger, T.F., Acosta, A.A., Simmons, K.F. et al. (1988) Predictive value of abnormal sperm morphology in in vitro fertilization. Fertil. Steril., 49, 112–117.[ISI][Medline]

Lipitz, S., Rabinovici, J., Ben-Shlomo, I. et al. (1993) Complete failure of fertilization in couples with unexplained infertility: implications for subsequent in vitro fertilization cycles. Fertil. Steril., 59, 348–352.[ISI][Medline]

Lipitz, S., Rabinovici, J., Goldenberg, M. et al. (1994) Complete failure of fertilization in couples with mechanical infertility: implications for subsequent in vitro fertilization cycles. Fertil. Steril., 61, 863–866.[ISI][Medline]

Liu, J., Nagy, Z., Joris, H. et al. (1995) Analysis of 76 total fertilization failure cycles out of 2732 intracytoplasmic sperm injection cycles. Hum. Reprod., 10, 2630–2636.[Abstract]

Mansour, R., Aboulghar, M., Serour, G. et al. (1995) The effect of sperm parameters on the outcome of intracytoplasmic sperm injection. Fertil. Steril., 64, 982–986.[ISI][Medline]

Molley, D., Harrison, K., Breen, T. and Hennessey, J. (1991) The predictive value of idiopathic failure to fertilize on the first in vitro fertilization attempt. Fertil. Steril., 56, 285–289.[ISI][Medline]

Nagy, Z., Liu, J., Joris, H. et al. (1995) The result of intracytoplasmic sperm injection is not related to any of the three basic sperm parameters. Hum. Reprod., 10, 1123–1129.[Abstract]

Nagy, Z., Janssenswillen, C., Janssens, R. et al. (1998) Timing of oocyte activation, pronucleus formation and cleavage in humans after intracytoplasmic sperm injection (ICSI) with testicular spermatozoa and after ICSI or in-vitro fertilization on sibling oocytes with ejaculated spermatozoa. Hum. Reprod., 13, 1606–1612.[Abstract]

Oehninger, S., Acosta, A.A., Morshedi, M. et al. (1988) Corrective measures and pregnancy outcome in in vitro fertilization in patients with severe sperm morphology abnormalities. Fertil. Steril., 50, 283–287.[ISI][Medline]

Oehninger, S., Kruger, T.F., Simon, T. et al. (1996) A comparative analysis of embryo implantation potential in patients undergoing in-vitro fertilization with a high insemination concentration or intracytoplasmic sperm injection. Hum. Reprod., 11, 1086–1089.[Abstract]

Olds-Clarke, P. (1996) How does poor motility alter sperm fertilizing ability? J. Androl., 17, 183–186.[Free Full Text]

Ombelet, W., Fourie, F.leR., Vandeput, H. et al. (1994) Teratozoospermia and in-vitro fertilization: a randomized prospective study. Hum. Reprod., 9, 1479–1484.[Abstract]

Ord, T., Patrizio, P., Balmaceda, J.P. and Asch, R.H. (1993) Can severe male factor infertility be treated without micromanipulation? Fertil. Steril., 60, 110–115.[ISI][Medline]

Palermo, G., Joris, H., Devroey, P. and Van Steirteghem, A. (1992) Pregnancies after intracytoplasmic sperm injection of a single spermatozoon into an oocyte. Lancet, 340, 17–18.[ISI][Medline]

Parinaud, J., Labal, B., Mieusset, R. et al. (1993) Influence of sperm parameters on embryo quality. Fertil. Steril., 60, 888–892.[ISI][Medline]

Payne, D. Flaherty, S.P., Jeffrey, R. et al. (1994) Successful treatment of severe male factor infertility in 100 consecutive cycles using intracytoplasmic sperm injection. Hum. Reprod., 9, 2051–2057.[Abstract]

Roest, J., Van Heusden, A.M., Zeilmaker, G.H. and Verhoeff, A. (1998) Treatment policy after poor fertilization in the first IVF cycle. J. Assist. Reprod. Genet., 15, 18–21.[ISI][Medline]

Ruiz, A., Remoh , J., Minguez, Y et al. (1997) The role of in vitro fertilization and intracytoplasmic sperm injection in couples with unexplained infertility after failed intrauterine insemination. Fertil. Steril., 68, 171–173.[ISI][Medline]

Staessen, C., Janssenswillen, C., Van den Abbeel, E. et al. (1993) Avoidance of triplet pregnancies by elective transfer of two good quality embryos. Hum. Reprod., 8, 1650–1653.[Abstract]

Svalander, P., Jakobsson, A.H., Forsberg, A.S. et al. (1996) The outcome of intracytoplasmic sperm injection is unrelated to `strict criteria' sperm morphology. Hum. Reprod., 11, 1019–1022.[Abstract]

Vandervorst, M., Tournaye, H., Camus, M. et al. (1997) Patients with absolutely immotile spermatozoa and intracytoplasmic sperm injection. Hum. Reprod., 12, 2429–2433.[Abstract]

Van Steirteghem, A.C., Joris, H., Liu, J. et al. (1995) Protocol for intracytoplasmic sperm injection. Hum. Reprod. Update, 1, No. 3, CD-ROM.

World Health Organization (1992) Laboratory Manual for the Examination of Human Semen and Sperm–Cervical Mucus Interaction, 3rd edn. Cambridge University Press, Cambridge.

Yang, D., Shahata, M.A., Al-Bader, M. et al. (1996) Intracytoplasmic sperm injection improving embryo quality: Comparison of the sibling oocytes of non-male-factor couples. J. Assist. Reprod. Genet., 13, 351–355.[ISI][Medline]

Submitted on March 4, 1999; accepted on June 1, 1999.