Human Reproduction vol.7 no.4 pp.537-544, 1992
Usefulness of partial dissection of the zona pellucida in a human in-vitro fertilization programme
P.Vanderzwalmen1, P.Barlow2, M.Nys, G.Bertin, F.Leroy2 and R.Schoysman Fertility and IVF Unit, Van Helmont Hospital, Vaarstraat, 42, 1800 Vilvoorde and 2FVF Clinic and Human Reproduction Research Unit, Saint Pierre Hospital, Free University of Brussels, Brussels, Belgium 'To whom correspondence should be addressed
The influence of partial zona dissection (PZD) on the fertilization rate was studied in 34 couples with a history of fertilization failure and/or severe sperm deficiency. Overall, PZD improved the rate of monospermic fertilization compared to controls (41/254 versus 6/111: P < 0.001) and fertilization was achieved in 50% of cases. However, the results differed according to the seminal characteristics. In 10 couples with at least two in-vitro fertilization (TVF) trials entailing total fertilization failure and with semen defined as normal, PZD did not significantly improve the monospermic fertilization rate (6/44 in the PZD group versus 2/39 among controls). A benefit related to PZD was evident in 33 attempts with severe sperm deficiency. In this group, only four of 72 unmanipulated control oocytes were fertilized but the monospermic fertilization rate was 14.6% for PZD oocytes. The rates of polyspermy were 40% and 14.6% in the groups with normal and abnormal semen parameters respectively. Of 33 trials with defective spermatozoa, 20 reached the stage of embryo transfer and three pregnancies were obtained, of which one aborted at 9 weeks. Key words: assisted fertilization/partial zona dissection/idiopathic infertility/semen parameters
Introduction In-vitro fertilization (TVF) has become an accepted treatment for couples with male infertility, the majority of whom suffer from varying degrees of oligozoospermia (Cohen etai, 1985). Frequently, the deficiency concerns various combinations of oligo-, astheno- or tetratozoospermia; in such cases, fertilization is infrequent and often absent (Overstreet et al., 1980). Apart from these evident abnormalities, a 'normal' semen analysis can also be associated with an absent or low fertilization rate (Huang and Yanagimachi, 1989; Salat-Baroux et al., 1990). Unexplained infertility may be related to abnormalities of the zona pellucida or to an inability of spermatozoa to penetrate the zona due to anatomical and functional acrosomal inadequacy (Jeyendran et al., 1985; Lalonde et al., 1988). With all these potential causes of infertility, the question arises as to whether assisted fertiliza© Oxford University Press
tion by micromanipulation could be a useful therapeutic strategy. Different microsurgical methods have been proposed to facilitate sperm passage through the zona pellucida. They include subzonal injection (Ng et al., 1988; Fishel et al., 1991), sperm injection directly into the ooplasm (Lanzendorf et al., 1988) and the creation of an opening in the zona pellucida, either chemically with acid Tyrode's solution (zona drilling, Gordon et al., 1988) or mechanically (partial zona dissection, PZD; Cohen et al., 1988). Each method has unique advantages and disadvantages, so we chose to apply the PZD technique in our human IVF programme for two reasons. Firstly, PZD afflicts the least trauma on the oocytes (Cohen et al., 1989) and had also been previously studied on mice in our laboratory (Barlow etai, 1991). Secondly, after the initial capacitation, no further sperm selection is performed and fertilizing spermatozoa will penetrate the opening in the zona pellucida without assistance. As first reported by Cohen et al. (1988) and Malter and Cohen (1989a,b) the PZD technique is successful in achieving healthy pregnancies in humans. Unfortunately, in these publications, the data on the severity of sperm characteristics were not very clear. Although the overall incidence of monospermic fertilization with abnormal spermatozoa was 56% for the PZD oocytes, a relatively high fertilization rate was observed in the non-manipulated group (47%) (Cohen et al., 1989) and the percentage of fertilization following PZD in men with abnormal semen was comparable to that of men with normal seminal parameters in conventional IVF (68%). Different seminological situations may account for the fact that these encouraging results could not be confirmed by other groups (Garrisi et al., 1990; Veiga et al., 1990; Simon et al., 1990). Recently, Cohen et al. (1991) also found a lower fertilization rate after PZD trials. Thus in general, low rates of fertilization have been reported and to date a very low pregnancy rate has been described (Veiga et al., 1990; Hill etai, 1991). Although PZD is successful in obtaining pregnancies in the human, the question remains whether discrepancies in the results are due to patient selection or to variation in the techniques. The aim of our study, therefore, was to evaluate the usefulness of PZD in treating different infertility criteria, based upon sperm parameters and/or previous failure of fertilization, in terms of fertilization and polyspermy rates, and embryo development and quality in a human IVF programme. Materials and methods Patients Forty-three attempts at PZD were performed in 34 couples having a long-standing history of infertility. In 10 couples, fertilization had failed in previous attempts despite normal sperm parameters. 537
P.Vanderzwalmen et al.
This group included cases of tubal (« = 3) and idiopathic infertility (n = 7) (Table I). Thirty-three attempts were performed in 24 patients with an identifiable 'male factor' of infertility, including oligozoospermia ( < 2 0 x 103 spermatozoa/ml), asthenozoospermia (
Usefulness of partial dissection of the zona pellucida in a human in-vitro fertilization programme
P.Vanderzwalmen1, P.Barlow2, M.Nys, G.Bertin, F.Leroy2 and R.Schoysman Fertility and IVF Unit, Van Helmont Hospital, Vaarstraat, 42, 1800 Vilvoorde and 2FVF Clinic and Human Reproduction Research Unit, Saint Pierre Hospital, Free University of Brussels, Brussels, Belgium 'To whom correspondence should be addressed
The influence of partial zona dissection (PZD) on the fertilization rate was studied in 34 couples with a history of fertilization failure and/or severe sperm deficiency. Overall, PZD improved the rate of monospermic fertilization compared to controls (41/254 versus 6/111: P < 0.001) and fertilization was achieved in 50% of cases. However, the results differed according to the seminal characteristics. In 10 couples with at least two in-vitro fertilization (TVF) trials entailing total fertilization failure and with semen defined as normal, PZD did not significantly improve the monospermic fertilization rate (6/44 in the PZD group versus 2/39 among controls). A benefit related to PZD was evident in 33 attempts with severe sperm deficiency. In this group, only four of 72 unmanipulated control oocytes were fertilized but the monospermic fertilization rate was 14.6% for PZD oocytes. The rates of polyspermy were 40% and 14.6% in the groups with normal and abnormal semen parameters respectively. Of 33 trials with defective spermatozoa, 20 reached the stage of embryo transfer and three pregnancies were obtained, of which one aborted at 9 weeks. Key words: assisted fertilization/partial zona dissection/idiopathic infertility/semen parameters
Introduction In-vitro fertilization (TVF) has become an accepted treatment for couples with male infertility, the majority of whom suffer from varying degrees of oligozoospermia (Cohen etai, 1985). Frequently, the deficiency concerns various combinations of oligo-, astheno- or tetratozoospermia; in such cases, fertilization is infrequent and often absent (Overstreet et al., 1980). Apart from these evident abnormalities, a 'normal' semen analysis can also be associated with an absent or low fertilization rate (Huang and Yanagimachi, 1989; Salat-Baroux et al., 1990). Unexplained infertility may be related to abnormalities of the zona pellucida or to an inability of spermatozoa to penetrate the zona due to anatomical and functional acrosomal inadequacy (Jeyendran et al., 1985; Lalonde et al., 1988). With all these potential causes of infertility, the question arises as to whether assisted fertiliza© Oxford University Press
tion by micromanipulation could be a useful therapeutic strategy. Different microsurgical methods have been proposed to facilitate sperm passage through the zona pellucida. They include subzonal injection (Ng et al., 1988; Fishel et al., 1991), sperm injection directly into the ooplasm (Lanzendorf et al., 1988) and the creation of an opening in the zona pellucida, either chemically with acid Tyrode's solution (zona drilling, Gordon et al., 1988) or mechanically (partial zona dissection, PZD; Cohen et al., 1988). Each method has unique advantages and disadvantages, so we chose to apply the PZD technique in our human IVF programme for two reasons. Firstly, PZD afflicts the least trauma on the oocytes (Cohen et al., 1989) and had also been previously studied on mice in our laboratory (Barlow etai, 1991). Secondly, after the initial capacitation, no further sperm selection is performed and fertilizing spermatozoa will penetrate the opening in the zona pellucida without assistance. As first reported by Cohen et al. (1988) and Malter and Cohen (1989a,b) the PZD technique is successful in achieving healthy pregnancies in humans. Unfortunately, in these publications, the data on the severity of sperm characteristics were not very clear. Although the overall incidence of monospermic fertilization with abnormal spermatozoa was 56% for the PZD oocytes, a relatively high fertilization rate was observed in the non-manipulated group (47%) (Cohen et al., 1989) and the percentage of fertilization following PZD in men with abnormal semen was comparable to that of men with normal seminal parameters in conventional IVF (68%). Different seminological situations may account for the fact that these encouraging results could not be confirmed by other groups (Garrisi et al., 1990; Veiga et al., 1990; Simon et al., 1990). Recently, Cohen et al. (1991) also found a lower fertilization rate after PZD trials. Thus in general, low rates of fertilization have been reported and to date a very low pregnancy rate has been described (Veiga et al., 1990; Hill etai, 1991). Although PZD is successful in obtaining pregnancies in the human, the question remains whether discrepancies in the results are due to patient selection or to variation in the techniques. The aim of our study, therefore, was to evaluate the usefulness of PZD in treating different infertility criteria, based upon sperm parameters and/or previous failure of fertilization, in terms of fertilization and polyspermy rates, and embryo development and quality in a human IVF programme. Materials and methods Patients Forty-three attempts at PZD were performed in 34 couples having a long-standing history of infertility. In 10 couples, fertilization had failed in previous attempts despite normal sperm parameters. 537
P.Vanderzwalmen et al.
This group included cases of tubal (« = 3) and idiopathic infertility (n = 7) (Table I). Thirty-three attempts were performed in 24 patients with an identifiable 'male factor' of infertility, including oligozoospermia ( < 2 0 x 103 spermatozoa/ml), asthenozoospermia (
