Hum. Reprod. Advance Access originally published online on April 26, 2008
Human Reproduction 2008 23(7):1633-1638; doi:10.1093/humrep/den135
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Age-specific success rate for women undertaking their first assisted reproduction technology treatment using their own oocytes in Australia, 2002–2005
1 Perinatal and Reproductive Epidemiology Research Unit, School of Women's and Children's Health, The University of New South Wales, McNevin Dickson Building, Randwick Hospitals Campus, Randwick, NSW 2031, Australia 2 Department of Obstetrics and Gynaecology, Faculty of Medicine, Monash University, Monash Medical Centre, 246 Clayton Road, Clayton, VIC 3168, Australia 3 School of Public Health and Community Medicine, The University of New South Wales, Sydney, NSW 2052, Australia
4 Correspondence address. Tel: +61-2-9382-1014; Fax: +61-2-9382-1025; E-mail: alex.wang{at}unsw.edu.au
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Abstract |
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BACKGROUND: Woman's age is an independent factor determining the success of assisted reproductive technology treatment. This study presents the age-specific success rate of first autologous fresh treatment in Australia during 2002–2005.
METHODS: This is a retrospective population-based study of 36 412 initiated first autologous fresh cycles conducted in Australian clinics during 2002–2005. Pregnancy and live delivery rates per initiated cycle were determined for each age.
RESULTS: The overall live delivery rate per initiated cycle was 20.4% with the highest success rate in women aged between 22 and 36 years. Male factor only infertility had a higher live delivery rate (22.0%) than female factor only infertility (19.2%). Advancing woman's age was associated with a decline in success rate. For women 
30 years, each additional 1 year in age was associated with an 11% (99% CI: 10–12%) reduction in the chance of achieving pregnancy and a 13% (99% CI: 12–14%) reduction in the chance of a live delivery. If women aged 35 years or older would have had their first autologous fresh treatment 1 year earlier, 15% extra live deliveries would be expected.
CONCLUSIONS: This study suggested that women aged 35 years or older should be encouraged to seek early fertility assessment and treatment where clinically indicated.
Key words: woman's age/autologous/pregnancy/live delivery/assisted reproductive technology
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Introduction |
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In general, younger women achieve higher rates of pregnancy and live births than their older counterparts (Menken et al., 1986
; Cnattingius et al., 1992; Dunson et al., 2004; Heffner, 2004; Joseph et al., 2005). However, in recent years, there has been a trend of women deferring childbirth. In the USA, the number of first births per 1000 women aged 35–39 years increased by 36% between 1991 and 2001, whereas the rate among women aged 40–44 years increased by 70% (Heffner, 2004). In Australia, one in eight (13.3%) first time mothers in 2005 was aged 35 years or older compared to 6.9% in 1995. Similarly, the average age of first time mothers increased by 2.2 years from 25.8 years in 1991 to 28.0 years in 2005 (Laws et al., 2007).
The aging of the general reproduction population has been paralleled by the increasing age of women undergoing assisted reproduction technology (ART) treatment. The average age of women who received In vitro fertilization (IVF) or micromanipulation in UK increased from 33.8 in 1992 to 34.8 in 2004 (Human Fertilisation and Embryology Authority, 2007). The average age of women who underwent ART treatment in Australia and New Zealand was 35.5 years in 2005, 0.3 years older than in 2002 (Wang et al., 2007).
The literature has shown that women seeking fertility treatment face the same age related issues as women conceiving naturally. It is likely that younger women who undergo ART treatment will have a better chance of getting pregnant and having a live delivery than older women (Kramer, 1987; Bai et al., 2002; Olivennes et al., 2002; Wang et al., 2007). Even though the success rate of ART has increased in recent years (Ciray et al., 2004; CDC, 2006), this rise in success rates has not been seen in older women. Since 2000, for women aged less than 35 years in the USA, the live birth rate per fresh non-donor cycle has increased from 33 to 37% in 2004, whereas it remains unchanged at about 4% for women aged 43 years or older (CDC, 2006).
Other female conditions, such as cause of infertility, previous pregnancies, obesity and chronic disease also contribute to the success of ART treatment (Tough et al., 2002, 2006; Bellver et al., 2006). On the other hand, these conditions, such as cause of infertility, are highly correlated with advancing age (Menken et al., 1986; Heffner, 2004; Baird et al., 2005). Studies have found that woman's age intersects with other demographic conditions in determining the success of fertility treatment (Heffner, 2004; Tufan et al., 2004; Baird et al., 2005).
What constitutes advancing age varies from study to study (Salihu et al., 2003), with the cut-off point usually at 35 (Prysak and Laros, 1995) or 40 years (Zaideh and Yahaya, 2001). Previously published papers classify patients into 5 year groups or other year groups dependent upon the conventions and population size. However, this lacks precision as success rates of ART treatment measured by clinical pregnancies and live deliveries per cycle vary by each year of age. The aim of this study is to provide comprehensive age-specific rates of pregnancy and live birth to assist couples in planning their reproductive future. In addition, the impact of cause of infertility on age-specific success rates was investigated. This study uses population data from the Australia and New Zealand ART Database (ANZARD) from 2002 to 2005 to provide the success rates in 1 year increments for women undergoing their first fresh ART treatment using their own oocytes.
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Materials and Methods |
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Data
Data and definitions used in this study are from the ANZARD, which are maintained at the National Perinatal Statistics Unit. ANZARD are collected annually, in de-identified format, from all fertility centers in Australia and New Zealand. ANZARD include information about the ART procedures, use of thawed embryos, blastocyst culture, embryo transfer and donation of gametes or embryos. It also includes information on pregnancy (ectopic pregnancy, spontaneous abortion and termination) and birth outcomes (gestational age, birthweight and perinatal mortality).
Data on women aged 18 years or older who had their first autologous fresh cycles in Australian clinics from 1 January 2002 to 31 December 2005, and subsequent pregnancy and birth outcomes were extracted from the ANZARD. Mixed fresh–thaw cycles, gamete intrafallopian transfer cycles, natural cycles and surrogacy cycles were excluded. A total of 36 412 women who had their first autologous fresh cycles are included in the final analysis.
Main outcome measures
Woman's age is calculated in completed years of age. Cause of infertility is classified as: male factor only infertility (a male factor problem was diagnosed and not any female factor problem), female factor only infertility (tubal disease, endometriosis or another female factor problem was diagnosed and not any male factor problem), combined male–female factor infertility (both male and female factor problems were diagnosed), unexplained infertility (neither a male nor female factor problem was diagnosed) and not stated (where cause of infertility was not reported to ANZARD).
Gestational age is defined as the completed weeks of gestation of the fetus and is calculated by (pregnancy end date – embryo transfer date) + 16 days. A clinical pregnancy was defined as one of the following criteria: evidence by ultrasound of intrauterine sac(s) or fetal heart(s); examination of products of conception reveal chronic villi; an ectopic pregnancy that had been diagnosed laparoscopically or by ultrasound. A delivery is defined as a birth event in which one or more baby was born of 20 weeks gestational age or of 400 g birthweight. A live delivery is a birth event in which one or more baby is live born of 20 weeks gestation or of 400 g birthweight.
An initiated cycle is defined as a cycle in which follicle-stimulating hormone was administered. The success was measured by live deliveries per initiated cycle.
Statistical analysis
Success rates were calculated for each woman's age and compared amongst cause of infertility. Because of small numbers, women aged 21 years or younger and women aged 45 years or older were grouped into two age groups. Logistic regression was used to investigate the odds of success in women aged 30 years or older. A further logistic regression model was built to illustrate the likelihood of success in 5 year age groups for women age 30 years or older compared to 25–29 years.
Two methods were tested to predict the number of live deliveries for the women aged 35–44 years if they undergo ART treatment 1, 2 or 3 years earlier. The first method directly applied the live delivery rate per initiated cycle of an age to 1, 2 or 3 years older. The second method built three logistic regression models for women aged 34–43, 33–42 and 32–41 years. The probability of live delivery at each age from the three logistic regression models is then applied to women aged 35–44 years, respectively. After comparing the two methods, the second method was more conservative and was used in the prediction.
Odds ratios (OR), adjusted odds ratios (AOR) (adjusted for cause of infertility) and 99% confidence intervals (99% CI) were calculated. Data were analysed with SPSS software (version 15.0; SPSS Inc, Chicago, IL, USA).
Ethics
Ethics approval for this study was granted by the Human Research Ethics Advisory Panel of the University of New South Wales, Australia.
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Results |
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The mean age of women having their first autologous fresh cycles was 34.4 years (SD 4.9 years), with about half of the women (47.4%) aged 35–44 years. About 12% (4321) of initiated cycles ended before oocyte pick-up, 87.0% (31 692) had oocytes collected and 75.7% (27 561) had an embryo transferred. One in four initiated cycles resulted in a clinical pregnancy, and one in five resulted in a live delivery. Nearly 17% of initiated cycles resulted in a singleton live delivery.
Table I details the outcomes of the first autologous fresh cycles and presents the age-specific rates of pregnancy and live delivery. Women aged 22–36 years achieved a clinical pregnancy rate per initiated cycle of 25% or higher at each age. However, the clinical pregnancy rate per initiated cycle declined with each advancing year of age from 30 years onwards and was most marked in women aged older than 35 years. For women aged 45 years or older, the average pregnancy rate was 1.9%.
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Women aged 22–36 years also had a higher rate of live deliveries per initiated cycle. Among this age group, the live delivery rate was above 20% at each age. The highest live delivery rate per initiated cycle was in women aged 24 years (30.3%). The live delivery rate decreased with increasing woman's age. For women aged 45 years or older, there was only one live delivery of 471 initiated cycles (Table I).
Table I also compares the live delivery rate per initiated cycle by cause of infertility at each age. Overall, couples with male factor only infertility achieved higher live delivery rate (22.0%) than those who had female factor only infertility (19.2%) or combined male–female factor infertility (18.4%).
Fig. 1 illustrates the pregnancy outcomes by woman's age. Over all, with advancing woman's age, the proportion with deliveries decreased and the proportion with spontaneous abortions increased. For women aged in their 20s to early 30s, less than 15% pregnancies ended in a spontaneous abortion and more than 80% resulted in a delivery. However, there is a marked increase in spontaneous abortion and decrease in delivery for women aged 36 years onward. In women aged 
42 years, the proportion of delivery was higher than the proportion of spontaneous abortion, while from age of 43 onward, proportionally more spontaneous abortions than deliveries were observed (29.5% of the 78 pregnancies resulted in a delivery and 66.7% were spontaneous abortions).
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The ectopic pregnancies and terminations were around 1.2% in women aged in theirs 20s, 1.5% in women aged in their 30s and above 3.8% in women aged 40 years or older.
To assess the impact of each additional 1 year of age on pregnancy and live delivery, a logistic regression model adjusted for cause of infertility was conducted for women aged 30 years or older. For each 1 year increment in woman's age, the chance of clinical pregnancy decreased 0.89 times and the chance of a live delivery decreased 0.87 times (Table II).
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A further logistic model was established to investigate the odds of getting pregnant and having a live delivery in women aged 30 years or older compared to those aged 25–29 years. Women aged 30–34 years had similar chance of pregnancy and live delivery compared to women aged 25–29 years. Women aged 35–39 years were 34% less likely to achieve clinical pregnancy and 39% less likely to have a live delivery compared to women aged 25–29 years. While, compared to women aged 25–29 years, women aged 45 years or older were 96% less likely to get pregnant and 99% less likely to have a live delivery (Table II).
Table III presents the predicted number of live deliveries for women aged 35–44 years if they underwent first autologous fresh treatment 1, 2 or 3 years earlier. If these women had treatment 1 year earlier, a total of 363 estimated extra live deliveries would be achieved. If they had treatment 2 years earlier or 3 years earlier, 749 or 1099 extra live deliveries would be expected, respectively.
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Fig. 2 illustrates the percentage of extra live deliveries predicted at each age if women aged 35–44 years who had first autologous fresh treatment 1, 2 or 3 years earlier. If 35 year old women would have had treatment 1 year earlier, about 15% extra live deliveries would be expected. If they had treatment 2 or 3 years earlier, 22 or 26% extra live deliveries would be expected, respectively. However, if 43 years old women had treatment 1 year earlier, 236% extra live deliveries would be expected. If 44 years old women had treatment 1 year earlier, 375% extra live deliveries would be expected.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionAuthor roleFundingAcknowledgementsReferences |
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This large Australian study confirms that in women undergoing fertility treatment advancing woman's age is one of the most important factors in determining the success of the first autologous fresh cycle. The findings reinforce the important fertility preservation message that women and couples with infertility problems need to have them diagnosed early and treated expeditiously if clinically indicated. It also shows that irrespective of the cause of infertility or which partner has the condition, each additional year of woman's age results in a relative decline in fertility. The rising proportion (from 6.9% in 1995 to 13.3% in 2005) of women having their first baby aged 35 years or older in Australia suggests that a misperception remains in the community of women's ability to conceive spontaneously with advancing age.
Among the first autologous fresh cycles, the highest success rates were in women aged between 22 and 36 years in which the clinical pregnancy rate per initiated cycle was above 25% at each age, and the live delivery rate per initiated cycle was above 20% at each age. However, the success rates declined with the increase in woman's age from 35 years onward. For women aged 45 years or older, the success rate was one live delivery of 471 initiated cycles.
Woman's age is an independent factor for pregnancies and perinatal outcomes (Heffner, 2004; Joseph et al., 2005; Wang et al., 2005). Advancing woman's age itself leads to declining fertility by reducing the quality of oocyte and lowering female hormones (Tufan et al., 2004; Baird et al., 2005). With the increase in woman's age, the fertility rate decreases from 400 pregnancies per 1000 married women aged <30 years to 100 per 1000 married women aged 45 years or older (Menken et al., 1986; Heffner, 2004). In our study, the clinical pregnancy rate for women aged less than 30 years was 321 pregnancies per 1000 initiated cycles, and decreased to 19 pregnancies per 1000 initiated cycle for women aged 45 years or older.
Advancing woman's age not only leads to declining fertility, but also pregnancy complications and spontaneous abortion (Nybo Andersen et al., 2000; Heffner, 2004). Nybo Andersen reported that the spontaneous abortion rate in women aged in their 20s and early 30s was about 13%, but increased to 25% in women aged 35–39 years, 50% in 40–44 years old women, and more than 90% in women aged 45 or older (Nybo Andersen et al., 2000). Consistent with a Centers for Disease Control report (CDC, 2006), this study found that the rate of spontaneous abortion in women aged less than 35 years is similar to Andersen's study, but in women aged 35 years or older, it is lower than in Andersen's study. One explanation is that intensive antenatal care was more common in ART pregnancies compared to natural pregnancies (Koivurova et al., 2002).
This study indicates that couples with any female factor infertility had lower success rates compared to those with male factor only infertility. As other studies have found, the lower occurrence of pregnancy was most likely associated with the pathological characteristics of women with female factor causes of infertility, such as tubal disease, endometriosis or hormonal disorders (Wisanto et al., 1995; Govaerts et al., 1998). Tan and colleague's study also suggested that, even when a pregnancy is achieved, female factor infertility would lead to a higher risk for hypertension and bleeding, which can in turn reduce the chance of live delivery (Tan et al., 1992). In women with normal fertility, once male factors are overcome, a better chance of pregnancy and live delivery can be expected.
The models show the effect on the number of live deliveries when treatment is 1, 2 or 3 years earlier. It reconfirms the need for primary care clinicians to refer couples for fertility assessment and treatment as soon as possible. If women aged 35 years or older had a first autologous fresh cycle 1 year earlier, the number of expected live deliveries would increase by 15% compared with the observed number. If they had treatment 2 or 3 years earlier, 30 and 44% increases in live deliveries would be expected. However, this study was unable to model the likelihood of spontaneous pregnancy among women who had had their first autologous fresh treatment, and hence the models would overestimate the predicted effects of earlier treatment. Several studies have reported spontaneous pregnancy in subfertile couples (Dunson et al., 2004; Hunault et al., 2004; van der Steeg et al., 2007). Van Der Steeg et al. found that 20% of subfertile couples had a spontaneous pregnancy in the 1 year follow-up with around 18% resulting in a live delivery. Hunault et al. and Dunson et al. found that in subfertile couples, advancing woman's age is independently associated with decreasing spontaneous pregnancy. These studies also indicate that couples should be encouraged to seek fertility assessment earlier.
This study retrospectively investigated age-specific success rates at a population level. Because of the large study population and the national coverage, bias would be less than that experienced at the clinic level. One limitation of this study is that the duration of subfertility and intention to treat are not available in ANZARD. Longer duration of subfertility would independently lead to decreases in rates of spontaneous pregnancy and ART related pregnancy (Templeton et al., 1996; te Velde et al., 2000; Dunson et al., 2004; Hunault et al., 2004). For women who have failed to conceive naturally over a 1 year period, the probability of spontaneous pregnancy in the subsequent year is 49%, and it declines to 14% for women who have not had pregnancy over a 3 year period (te Velde et al., 2000). Templeton et al. found a significant decrease in age-adjusted live birth rate per treatment cycle with increasing duration of infertility between 1 and 12 years.
Another limitation of this study is the potential variability in case reporting. The follow-up information on pregnancy and birth outcomes was collected in a number of ways including follow-up by the treatment doctors and self-reported by patients to fertility clinics. During 2002–2005, information on pregnancy and birth outcomes was not stated for 0.1% of first autologous fresh cycles.
The effectiveness of first autologous fresh ART treatment declines with advancing woman's age. There has been debate in Australia about whether age restriction should be introduced. The Australian policy recommends that it is not clinically appropriate to initiate a new cycle of in IVF treatment in women using their own oocytes at 44 years and over (Australian Government Department of Health Aging, 2006). The Practice Committee of the American Society for Reproductive Medicine (2006) suggests that evaluation and treatment of infertility should not be delayed in women 35 years and older. This study shows that, when the first autologous fresh treatment is at 43 years of age, 6% of initiated cycles result in a clinical pregnancy, but nearly 60% of those pregnancies end in spontaneous abortions. From the unadjusted age-specific rates in this study, first autologous fresh treatment at 42 years would give an overall 8% rate of clinical pregnancies per initiated cycle, and proportionally more pregnancies resulting in a delivery rather than a spontaneous abortion. However, woman's age is not the only independent factor in predicting the success of ART treatment. A decision to treat and subsequent outcome also depends on the duration and type of subfertility, the chance of spontaneous pregnancy, and the result of fertility assessment, including post-coital and ovarian reserve testing (Hunault et al., 2004; Tufan et al., 2004; Ludwig et al., 2005).
The results of this study suggest that couples should be encouraged not to delay childbearing, because the chances of becoming pregnant by ART treatment or spontaneously decline every year, especially after age 35 years. Women aged 35 years or older who want to have a baby should be encouraged to seek a fertility assessment as early as possible and treatment where clinically indicated.
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All authors have contributed to the conducting of this study. The manuscript has been seen and approved by all authors. Y.A.W. involved in study design, method investigation, data analysis and preparing the manuscript. D.H. involved in study design, method investigation and review of the manuscript. D.B. involved in method investigation, data analysis and review of the manuscript. E.A.S. involved in study design, method investigation and review of the manuscript.
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Funding |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionAuthor roleFundingAcknowledgementsReferences |
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Fertility Society of Australia funds the ANZARD collection. The Australian Institute of Health and Welfare provides core funding for the AIHW National Perinatal Statistics Unit.
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Acknowledgements |
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The Fertility Society of Australia is the funding body for the Australian and New Zealand Reproductive Technologies Database (ANZARD). The authors acknowledge the contribution of Australian fertility clinics in the provision of data to ANZARD.
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References |
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Submitted on November 2, 2007; resubmitted on March 19, 2008; accepted on April 1, 2008.
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