Centre for Reproductive Medicine, Dutch-speaking Brussels Free University, Laarbeeklaan 101, B 1090 Brussels, Belgium
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Abstract |
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Key words: age/cumulative pregnancy rates/delivery/ICSI/life-table analysis
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Introduction |
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Materials and methods |
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The rank of trial ranged from 18 per couple; the average rank of trial was 1.9. The main outcome measure was any delivery after 25 weeks gestation. Patients were not re-enrolled after a first delivery. The indications for ICSI were long-standing male infertility or fertilization failure after conventional IVF. Cumulative delivery rates were calculated by life-table analysis (Hull et al., 1992) in three age groups, namely 3839, 4043 and >43 years.
Pregnancy follow-up was documented by a prospective follow-up programme for ICSI (Bonduelle et al., 1999).
Contact was possible with 24 out of 188 patients who had stopped their treatment in our centre; the other 164 couples could not be reached either by telephone or letter for further follow-up. All of these couples were residents of another country. A complete follow-up was obtained for 64 patients (including 40 who delivered) out of 228 patients (28%).
Routinely, a long protocol was used, but exceptionally (in <1% of cycles) a short protocol was used in combination with a GnRH agonist, buserelin (Suprefact®; Hoechst, Frankfurt, Germany), and HMG (Humegon®; Organon, Oss, The Netherlands or Pergonal®; Serono, Geneva, Switzerland). The details of sperm and oocyte assessment and handling have been described extensively elsewhere (Van Steirteghem et al., 1996). The embryo transfer policy used has been described in detail previously (Adonakis et al., 1997
). However, in patients aged >40 years, up to six embryos were transferred into the uterine cavity 48 h after the sperm injection procedure. For luteal phase supplementation, micronized progesterone (600 mg/day; Utrogestan; Piette, Brussels, Belgium) was administered intravaginally in three separate doses with or without additional HCG (3x1500 or 5000 IU as a single dose; Pregnyl; Organon or Profasi; Serono) (Staessen et al., 1995
).
Cumulative delivery rates were calculated by life-table analysis using the KaplanMeier product limit procedure (Kaplan and Meier, 1958) and differences between groups were assessed by the log-rank test. A P-value of 0.05 was assumed to test for significance of differences in results. Cumulative delivery rates were expressed as cumulative percentage probabilities with their 95% confidence intervals (CI). These computational procedures were performed using Statistics Package for Social Sciences (SPSS) for Windows version 6.1 (SPSS Inc., Chicago, IL, USA).
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Results |
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In the 3839 years age group, the real cumulative delivery rate was 21%, and the expected delivery rate was 26% after two cycles, following which a plateau was reached.
In the 4043 years age group, the real cumulative delivery rate was 12%, and the expected delivery rate was 17% after three cycles, following which a plateau was reached. There was only one delivery in the >43 years age group, which comprised 26 patients who underwent a total of 66 cycles.
When all age groups were analysed together, the expected cumulative delivery rate was seen to increase up to the sixth cycle but, owing to the small numbers of patients, figures should not be considered as clinically relevant above four cycles.
Cumulative delivery rates according to age groups are shown in Table I. Life-table analysis of the real and expected cumulative delivery rates is shown in Figure 1
, together with the drop-out rates. The drop-out rate was ~40% per treatment cycle, and 60% of patients stopped treatment after their first two cycles. Reasons for withdrawal included: psychologically too heavy a treatment; too-advanced maternal age; and financial burden too high. An analysis of the computerized database showed that 36 of 228 patients (16%) stopped their treatment due to fertilization or cleavage problems. Increasing age did not influence the drop-out rate of patients. The tendency towards decreasing pregnancy rates with increasing female age was statistically significant (P = 0.0039). The 164 couples (72%) who were not contacted during follow-up were assumed not to be pregnant.
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Discussion |
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It is well known that increasing age is associated with a decrease in pregnancy rate, either in natural conception or after assisted reproductive techniques (Federation CECOS, 1982; Van Noord-Zaadstra et al., 1991
; Scott et al., 1995
; Devroey et al., 1996
; Grimbizis et al., 1998
). Ovarian reserve decreases with advancing age, leading to a decrease in the numbers of oocytes obtained (Faddy and Gosden, 1996
), an increase in the incidence of aneuploidy in oocytes (Munné et al., 1995
), and poor oocyte quality (Navot et al., 1991
). Age is therefore the most important limiting factor for the success of assisted reproduction in women aged >37 years. The onset of this phenomenon is individually variable (Grimbizis et al., 1998
), and there may therefore be a subgroup of patients with an adequate follicular response to stimulation yielding higher success rates after assisted reproduction (Vandervorst et al., 1997
; Grimbizis et al., 1998
).
In older women, up to six embryos were replaced back in the uterus, as the chance of chromosomally abnormal embryos increases with the patient's age. This in turn can result in a poor reproductive outcome, as most chromosomally abnormal embryos will not implant or will lead to miscarriage. Although increasing the number of embryos transferred may not have been standard practice in other centres at the time this study was performed, it is now known that at least 60% of embryos in women >37 years of age are chromosomally abnormal (Staessen et al., 2001). Therefore, in older women in whom no pre-implantation diagnosis is performed, it is justifiable to transfer more embryos after consulting the patient. This can increase the chance of conception without a proportional increase in the chance of multiple pregnancy.
It is widely accepted that non-ovarian factors have a limited effect on reproductive potential (Scott and Hofmann, 1995); for example, sperm parameters hardly influence the results of ICSI outcome (Nagy et al., 1995
; Osmanagaoglu et al., 1999
).
The findings of this study with regard to ICSI treatment in women aged >37 years are comparable with those from studies dealing with IVF. Most pregnancies were observed during the first four treatment cycles (Guzick et al., 1986; Haan et al., 1991
; Tan et al., 1992
). In a comparable study, only 14 patients aged >41 years among a total of 337 patients aged >36 years, had shown an ongoing pregnancy rate of 24% after two IVF/ICSI treatment cycles (Stolwijk et al., 2000
). These figures corroborate the findings of the present study, namely a 21% delivery rate in the group of women aged 3839 years. A delivery rate of 8.7% per embryo transfer in women aged 4044 years has also been reported by others (Lass et al., 1998
), and a comparable birth rate was observed in the present study in women aged 4043 years. Women aged >43 years appear not to have a realistic chance of delivery of a child, even after repeated cycles; indeed, only one delivery was observed out of 66 cycles in 26 patients aged
44 years. Some of these patients went through up to eight cycles, despite being aware of their limited chances. The findings of the present study corroborate those of others (Ron-El et al., 2000
), who did not record any deliveries in women aged >43 years among a group of 56 patients.
In a previous study published by our group on cumulative delivery rates in women aged <37 years, a decrease of 10% in real cumulative delivery rate was observed between the age groups of 2029, 3034 and 3537 years. While in the 3537 years age group the real cumulative delivery rate was 45%, it fell to 24% in the present study in women aged 3839 years (Osmanagaoglu et al., 1999).
Three twin pregnancies occurred among patients aged 40 years. In a previous study, six triplet and 48 twin pregnancies were reported out of 298 deliveries in women aged <37 years (Osmanagaoglu et al., 1999
).
It has been suggested (Engmann et al., 1999) that when calculating cumulative delivery rates by life-table analysis, the age of each woman should be recorded at the start of her first treatment cycle, though this causes an underestimation of age-related cumulative pregnancy rates. For example, when a woman starts her first treatment at 34 years, her second at 37 years and her third at 40 years, calculation of the cumulative pregnancy rate will consider her to be 34 years. This calculation method introduces a biased decrease due to advancing female age (Engmann et al., 1999
). In order to minimize this pitfall, the reproductive period was divided into six age groups. The first three groups, which represent the most fertile period of reproductive life, have already been described (Osmanagaoglu et al., 1999
; Figure 2
). Discontinuation of treatment because of poor outcome was seen in only 2.6% of patients aged <37 years (Osmanagaoglu et al., 1999
). As expected in patients aged >37 years, the drop-out rate was much higher; moreover, 16% (36/228) of the patients discontinued their treatment due to fertilization or cleavage problems. Consequently, in this group of patients the application of life-table analysis may indeed overestimate the expected results.
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In limiting our findings to subgroups of at least 30 patients, it may be concluded that after three ICSI cycles, the real cumulative delivery rate reached a plateau at 15% in women aged >37 years. However, an expected cumulative delivery rate of 21% may be obtained at the end of the third cycle, assuming that no selective drop-outs occur. Women aged >43 years do not have a realistic chance of achieving a delivery using their own oocytes. The present results show a real and expected cumulative delivery rate of 2% after three cycles. This analysis provides an important means of counselling patients about their chances of achieving a delivery by ICSI when they are aged >37 years.
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Acknowledgements |
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Notes |
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References |
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Submitted on February 13, 2001; resubmitted on August 28, 2001; accepted on November 28, 2001.