|Year : 2017 | Volume
| Issue : 4 | Page : 204-209
Analysis of factors influencing the cumulative pregnancy outcome of In Vitro fertilization-embryo transfer in women aged 35 years and older with normal ovarian reserve
Meng Zhang1, Tao Bu2, Hai-Qing Tian1, Xia Li1, Xiao-Hui Wan1, Xin-Min Mao1, Qing-Li Wang1, Xiao-Lin La1
1 Centre of Reproductive Medicine, The First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang 830011, China
2 Centre of Information and Statistics, The First Affiliated Hospital of Xinjiang Medical University, Xinjiang 830011, China
|Date of Submission||27-Oct-2017|
|Date of Web Publication||7-Feb-2018|
Department of Reproductive Medicine, The First Affiliated Hospital of Xinjiang Medical University, Xinjiang 830011
Source of Support: None, Conflict of Interest: None
Background: To investigate the factors associating with the cumulative clinical pregnancy outcome of in vitro fertilization-embryo transfer (IVF-ET) in women aged 35 years and older with normal ovarian reserve.
Methods: A total of 358 patients undergoing IVF-ET at the Department of Reproductive Medicine, the First Affiliated Hospital of Xinjiang Medical University between January 2014 and June 2016 were analyzed by the Kaplan–Meier method and Cox proportional hazards model.
Results: The probability of pregnancy in women 35–37 years of age and 38–40 years of age was 75.9% (95% confidence interval [CI]: 75.1%–76.7%) and 66.9% (95% CI: 65.6%–68.2%), respectively, and it was 37.8% (95% CI: 34.7%–41.1%) in women aged 40 years and older. Univariate analysis (hazard ratio [HR]: 2.50, 95% CI: 1.647–3.774) and multivariate analysis (HR: 2.17, 95% CI: 1.427–3.268) showed a correlation between the number of retrieved oocytes and successful pregnancy.
Conclusions: The number of retrieved oocytes plays a key role in the pregnancy outcome of women aged 35 years and older with normal ovarian reserve. We recommend the number of retrieved oocytes be increased for women aged 35 years and older with normal ovarian reserve.
Keywords: Cumulative Pregnancy Outcome; In Vitro Fertilization-Embryo Transfer; Normal Ovarian Reserve; Women Aged 35 Years and Older
|How to cite this article:|
Zhang M, Bu T, Tian HQ, Li X, Wan XH, Mao XM, Wang QL, La XL. Analysis of factors influencing the cumulative pregnancy outcome of In Vitro fertilization-embryo transfer in women aged 35 years and older with normal ovarian reserve. Reprod Dev Med 2017;1:204-9
|How to cite this URL:|
Zhang M, Bu T, Tian HQ, Li X, Wan XH, Mao XM, Wang QL, La XL. Analysis of factors influencing the cumulative pregnancy outcome of In Vitro fertilization-embryo transfer in women aged 35 years and older with normal ovarian reserve. Reprod Dev Med [serial online] 2017 [cited 2021 Jan 25];1:204-9. Available from: https://www.repdevmed.org/text.asp?2017/1/4/204/224913
Meng Zhang and Tao Bu contribute equally to this work.
| Introduction|| |
In general, age determines whether a woman will deliver a healthy child by either natural procreation or assisted reproduction. With the natural decline in female fertility with increasing age, there has been a steady increase in the number of women seeking assisted reproductive technology to become clinically pregnant.
Due to the lifting of the universal two-child policy, a large number of women with age older than 35 would like to have another child. Research showed that a woman's fertility began to decrease at the age of 30, declined even more significantly after the age of 35, and then began to disappear after the age of 40. Results indicated that the live birth rate among women aged 39 years and younger is equal or higher than that reported in the general population, that is, if these women are treated with up to six in vitro fertilization (IVF) cycles. Besides the chronological age, ovarian reserve plays a critical role in pregnancy outcomes, and women with normal ovarian reserve may have improved chances of pregnancy. Therefore, older women with normal ovarian reserve should not be denied IVF treatment.
Multiple factors affect the success of IVF treatment, such as the female's age, ovarian reserve, and treatment regimen. The three regimens for women older than 35 years of age with poor ovarian response are the long gonadotropin-releasing hormone (GnRH) agonist regimen, short GnRH agonist regimen, and GnRH antagonist regimen, and the long protocol is the most effective.,,, To date, there is no study involving women aged 35 years and older with normal ovarian reserve. Therefore, the aim of this study was to investigate the factors that affected the pregnancy outcomes in women older 35 years of age with normal ovarian reserve and provide insights on the best treatment regimen.
| Methods|| |
Study design and participants
A retrospective cohort study was performed. This study involved women undergoing IVF cycles between January 1, 2014, and June 31, 2016 at the Center of Reproduction, the First Affiliated Hospital of Xinjiang Medical University. Women aged 35 years and older undergoing IVF-ET and meeting the inclusion and exclusion criteria were included. The inclusion criteria were as follows: (1) an anti-Müllerian hormone level of 1.0–4.0 μg/L; (2) an antral follicle count (AFC) between 7 and 14; and (3) a basal follicle-stimulating hormone (FSH) level <10 IU/L. The exclusion criteria were as follows: (1) patients undergoing fresh IVF cycles without embryo transfer (ET) due to fertilization failure or other reasons; (2) patients with congenital uterine dysplasia; (3) patients with polycystic ovary syndrome; (4) patients with severe disease that is not suitable to receive IVF; and (5) patients with chromosome abnormalities. The study was approved by the Ethics Review Board of the First Affiliated Hospital of Xinjiang Medical University, and all participants signed the inform consent before the study.
Data were retrieved from a clinical database available at the Reproductive Medicine Center and the following variables were included: maternal age, paternal age, basal FSH, basal luteinizing hormone (LH), body mass index (BMI), duration of infertility, number of retrieved oocytes, Gn dosage, Gn day, and other indicators. At the same time, ovarian stimulation protocol was recorded; the protocol was divided into the long GnRH agonist regimen and GnRH antagonist regimen. The primary endpoint, clinical pregnancy, was defined as the presence of a gestational sac in the uterine cavity at 4 weeks after ET, as detected on ultrasonography. All pregnancy outcomes were assessed through a review of medical records. All participants were followed for at least 12 months to ensure that all embryos were implanted, unless the participants discontinued treatment.
The long GnRH agonist regimen was as follows: pituitary downregulation with triptorelin (Decapeptyl ®, Ferring AG, Switzerland) at 0.1 mg/d by subcutaneous injection in the mid-luteal phase of the menstrual cycle, which was continued for 2 weeks. This regimen was tracked according to hormonal levels, an ultrasound confirmation of downregulation, and recording of the AFC, after which ovarian stimulation was commenced with exogenous gonadotropin injections at a dose of 112.5–225 IU/day and continued triptorelin at 0.1 mg/d until the administration of human chorionic gonadotropin (hCG).
The GnRH antagonist regimen was as follows: according to the multiple-dose protocol, in which exogenous gonadotropins injections at a dose of 112.5–225 IU/day were started on day 3 and later 0.25 mg s.c. of cetrorelix (Cetrotide ®, Merck Serono Europe Limited) was added daily when the leading follicle achieved to 14 mm until the administration of hCG.
In both stimulation regimens, all patients received an initial gonadotropin dose of 112.5–225 IU of exogenous gonadotropins for the first 5 days, followed by individual adjustments in gonadotropin dose based on the ovarian response and estradiol concentration. When the leading follicle reached about 17–18 mm in diameter, 10,000 IU hCG or 250 μg recombinant hCG was administered by subcutaneous injection, which was followed 34–36 h later by an ultrasound-guided transvaginal oocyte aspiration.
For patients who were received the fresh-ET regimen: luteal support was initiated on the day after oocyte retrieval as follows: dydrogesterone (Duphaston ®, Abbott) in an oral formulation at 10 mg was administered every 8 h and progesterone sustained-release vaginal gel (Crinone ®, Merck Serono Limited, UK) at 90 mg was administered until a negative pregnancy test or until 10 weeks after conception.
For patients who were received the frozen-ET regimen: no luteal phase support was administered after oocyte retrieval, and day-3 embryos were cryopreserved for later transfer. Oral estradiol valerate (Progynova, Delpharm Lille) was administered for endometrial preparation on day 2 or 3 of the menstrual cycle until 4 weeks after the frozen-ET. Dydrogesterone and progesterone sustained-release vaginal gels were added when the endometrial thickness reached 8 mm or more or at the physician's discretion if the thickness of the endometrium was less than 8 mm. On day 4 of the progesterone regimen, one or two day-3 frozen embryos were thawed and transferred. The luteal phase support with dydrogesterone and progesterone sustained-release vaginal gel continued until 10 weeks after gestation.
All values were expressed as percentages or means ± standard deviation. Differences between groups were analyzed by the Chi-square test for categorical variables or t-test for continuous variables. Changes in values before and after therapy were analyzed by the paired Student's t-test.
The cumulative probability of pregnancy for each couple undergoing treatment during the study period was estimated by the Kaplan–Meier method with censored data for patients who did not return for treatment when no pregnancy outcome was observed. This was according to the sum of the ET in each set of treatments required to reach a pregnancy outcome, which was defined as a set of consecutive IVF cycles including fresh and frozen/thawed embryo replacements performed in a patient until she discontinued treatment or achieved clinical pregnancy. No participants were omitted from this study because Kaplan–Meier analysis allowed the statistical computation of these cases, and they were computed until the moment they abandoned.
The cumulative pregnancy probability and pregnancy outcomes were determined by Kaplan–Meier survival analyses and supplemented by the log-rank, Breslow, and Tarone-Ware tests for comparing the survival curves according to each specific group. Variables were assessed by univariate and multivariate analyses with the use of a Cox proportional hazards model to evaluate the factors that could affect pregnancy outcome. A stepwise regression procedure was used to determine which factors were major independent predictors for survival. A two-tailed P < 0.05 was considered to be significant in all analyses. All analyses were performed using R version 3.3.1 (http://www.r-project.org/).
| Results|| |
A total of 358 participants with age ≥35 years old were categorized into pregnant group (n = 168) and nonpregnant group (n = 190). The cumulative pregnancy rate was 47.0%. There was no statistical significance in the maternal age, paternal age, basal FSH level, basal LH level, basal E2 level, BMI, infertility duration, number of retrieved oocytes, Gn dosage, Gn day, and other clinical and laboratory indexes between groups [Table 1].
|Table 1: Clinical characteristics and pregnancy outcomes (x¯ ± s, M [P25, P75])|
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[Figure 1] shows that there was no significant difference between the long GnRH agonist regimen and GnRH antagonist regimen. For categorized Gn days, [Figure 2] shows that there was no difference in this category. [Figure 3] shows the cumulative probability of pregnancy according to age, that is, the pregnancy rate decreased significantly as the patient age increased. The probability of pregnancy in participants with 35–37 years of age and 38–40 years of age was 75.9% (95% confidence interval [CI]: 75.1%–76.7%) and 66.9% (95% CI: 65.6%–68.2%), respectively, and it dramatically decreased to 37.8% (95% CI: 34.7%–41.1%) in participants aged 40 years and older. The numbers of retrieved oocytes were significantly different between groups, and the P value of the Log-rank test was 0.0445 [Figure 4].
|Figure 1: Kaplan–Meier curves depending on the total number of transferred embryos required to achieve a pregnancy by the protocols.|
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|Figure 2: Kaplan–Meier curves depending on the total number of transferred embryos required to achieve a pregnancy categorized by the gonadotropin days.|
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|Figure 3: Kaplan–Meier curves depending on the total number of transferred embryos required to achieve a pregnancy categorized by the age.|
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|Figure 4: Kaplan–Meier curves depending on the total number of transferred embryos required to achieve a pregnancy categorized by the number of retrieved oocytes.|
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[Table 2] illustrates that only the number of retrieved oocytes was associated with successful pregnancy by univariate analysis (hazard ratio [HR]: 2.50, 95% CI: 1.647–3.774) and multivariate analysis (HR: 2.17, 95% CI: 1.427–3.268). The maternal age (for 38–40 years vs. 35–37 years: HR: 1.04, 95% CI: 0.759–1.418; for >40 years vs. 35–37 years: HR: 0.68, 95% CI: 0.446–1.046), ovulation induction protocol (HR: 1.04, 95% CI: 0.736–1.460), and Gn day (for 10–12 days vs. ≤9 days: HR: 0.81, 95% CI: 0.906–1.695; for ≥13 days vs. ≤9 days: HR: 0.97, 95% CI: 0.732–1.299) were not associated with pregnancy outcomes.
|Table 2: Predictors for survival by univariate and multivariate analyses|
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| Discussions|| |
This study was designed to investigate the factors influencing the cumulative pregnancy outcome in subfertile women aged 35 years and older with ovarian normal response. A total of 358 women met the inclusion criteria. Among these, 168 women achieved successful pregnancy, whereas 190 women failed to do so (the cumulative pregnancy rate was 47.0%). Univariate and multiple analyses showed a strong association between the number of oocytes transferred and pregnancy.
After 35 years of age, the number of follicles decreased dramatically, and eggs will more likely to have abnormal nuclei (including spindle abnormalities and aneuploidy abnormalities) that may result in chromosomal abnormalities and meiosis errors. Studies reported that the quality of granulosa cells decreased with increasing age, thus affecting the health of oocytes.,,, Thum et al. suggested that women older than 38 years of age who underwent IVF-ET have a lower pregnancy rate. However, in our study, there was no statistical significance when the 38–40 years group was compared with the reference group. The inconsistent results might be due to the patients with normal ovarian reserve that were included in our study. Our results demonstrated that the cumulative probability of pregnancy did increase with the increased number of retrieved oocytes for women with normal ovarian reserve, and that age was not the only factor. Therefore, women could increase their probabilities of pregnancy through increasing the number of retrieved oocytes, especially for those women aged between 35 and 40 years old.
Several studies indicated that different protocols can also affect pregnancy outcomes.,, However, we did not observe a difference between the long GnRH agonist regimen and the GnRH antagonist regimen, which might have been due to the normal ovarian reserves of all participants in our study. For these two regimens, the probability of pregnancy increased with increasing number of retrieved oocytes. Similar results were also reported by Tigges et al. and Garrido et al., Although Gn days are variable for different regimens, one study suggested that a high-dose Gn negatively affects the endometrium and pregnancy outcomes. Pal et al. reported that a high-dose Gn decreases the cycle cancellation rate but increases the oocyte retrieval rates. However, the pregnancy rate and live birth rate decrease markedly, and the possibility of a spontaneous abortion increases. Our results demonstrated that there was no difference among the three Gn day subgroups and that our results are similar with Martin et al., but different from those of Chuang et al. This might be due to the heterogeneous patient population, such as the BMI of our study was 22.7 kg/m2 but it was 25.6 kg/m2 in their study.
The GnRH antagonist regimen had fewer Gn days than the long GnRH agonist regimen, which reduced costs and saved time for patients. Therefore, it might be a better choice for women over 35 years with normal ovarian reserve.
There were several limitations in this study. This was a retrospective study that used data from a single center. Therefore, the sample size was relatively small, especially in women older than 40 years. Furthermore, we speculated that the conclusion of this study might be affected by the limitation of the control for unknown factors or confounders that could have played a role in clinical decisions. A multicenter randomized controlled clinical trial with a larger sample size is needed in the future to provide more decisive answers on how these factors affected the success of pregnancy.
In summary, the number of retrieved oocytes plays a key role in the pregnancy outcome of women aged 35 years with normal ovarian reserve. We recommend that the number of retrieved oocytes be increased for women aged 35 years and older with normal ovarian reserve.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]