Aim
This retrospective cohort study aimed to comprehensively evaluate the laboratory and clinical outcomes of different oocytes retrieved from PCOS patients aged <35 years who underwent assisted pregnancy using the follicular phase long-acting long protocol and to discuss the optimum number of oocytes in this population.
Patients
The protocol of this retrospective cohort study was approved by the Ethical Review Committee of the First Affiliated Hospital of Zhengzhou University. Written informed consent was waived due to the retrospective nature of the study. The selected research participants were patients who underwent IVF/ICSI at the Reproductive Medicine Center of the First Affiliated Hospital of Zhengzhou University between January 2017 and June 2019. The clinical data of the patients were assessed in the first cycle of IVF/ICSI-assisted pregnancy.
All patients were younger than 35 years, diagnosed according to the Rotterdam criteria for PCOS, and undergoing their first IVF/ICSI cycle with the follicular phase long-acting long protocol. For the purposes of this study, patients with cycles involving oocyte donation, rescue ICSI, uterine abnormalities, and without retrieved oocytes were excluded from the analysis. Patients who had not gotten pregnant after 2 years but still had frozen embryos remaining were also excluded from the study. Therefore, the study included 1816 patients with one complete round of treatment with a fresh transfer cycle and subsequent frozen embryo transfer (ET) cycles.
In this study, patient characteristics, including age, body mass index (BMI), duration of infertility, type of infertility, anti-Müllerian hormone (AMH) levels, and follicle-stimulating hormone (FSH) levels, were evaluated. Data regarding other parameters, including gonadotropin dose, number of days of ovarian stimulation, number of oocytes retrieved, type of insemination, and fertilization rate, were also recorded. The primary outcome was the cumulative live birth rate.
IVF/ICSI-ET
Downregulation protocol: On the second to third days of menstruation, the patients were subcutaneously injected with a long-acting GnRH agonist (Diphereline, 3.75 mg; Beaufour Ipsen Industrie, Dreux, France). Thirty days later, blood samples were obtained from the patients to determine the serum levels of FSH, luteinizing hormone (LH), E2, and progesterone. The sizes of the antral follicles were monitored via vaginal ultrasonography. The COH was initiated when the FSH level was <5 IU/L, the LH level was <3 IU/L, and the antral follicle was nearly 5 mm in diameter.
COH protocol: The individualized dosage of gonadotropin (GONAL-f; Merck Serono, Darmstadt, Germany) was determined based on the patient’s age, AMH level, antral follicle count (AFC), BMI, and serum FSH level.
hCG injection and corpus luteum support standard: We administered 250 μg of Azer (Merck Serono, Italy) and 2000 IU of hCG (Zhuhai Livzon Pharmaceutical) when the diameter of one dominant follicle was ≥20 mm, the diameters of three follicles were ≥17 mm, or two-thirds of the follicles had diameters ≥16 mm. The eggs were harvested under vaginal ultrasound guidance 36–37 h after the injections were administered.
Fresh ET: The method of fertilization was based on semen quality. Fresh ET was performed 3–5 days after the oocyte retrieval based on embryo quality, endometrial status, and conditions of the patients. The transplant was cancelled if the patients were deemed to be at high risk for OHSS, the P level was >3 ng/mL, or a uterine effusion was demonstrated. Depending on the specific situation of each patient, different frozen-thawed ET protocols were formulated [14].
Frozen-thawed ET: Depending on the specific situation of each patient, different frozen-thawed ET protocols were formulated. These mainly included the following three methods: natural cycle, hormone replacement cycle, and downregulated hormone replacement cycle.
Statistical analysis
The patients were categorized into seven groups according to the number of oocytes retrieved: group A, 1–5; group B, 6–10; group C, 11–15; group D, 16–20; group E, 21–25; group F, 26–30; and group G, >30. Continuous variables were first assessed for normality of distribution using the Kolmogorov–Smirnov test. Data with normal distributions are presented as means with their standard deviations, and skewed data are presented as medians with their interquartile ranges. One-way analysis of variance or the Kruskal–Wallis test was used to compare multiple sets of measurement data, and the chi-squared test or Fisher’s exact test was used to analyze multiple sets of count data, as appropriate. The results of count data are expressed as rates (%). Between-group comparisons were performed using the chi-squared test, and comparisons among multiple groups were performed using the chi-squared segmentation method. Regarding treatment cycles, upon dividing the data into seven groups according to the number of oocytes retrieved, important aspects of the treatment outcomes were assessed, including the fresh cycle pregnancy rate, cumulative pregnancy rate, “freezing all” rate for high ovarian response, and high-quality embryos rate. Logistic regression analyses were performed to identify independent correlates of each possible confounding factor, particularly “freezing all” rate for high ovarian response and cumulative pregnancy outcomes after adjusting for other confounders identified in the univariate analysis. The number of oocytes retrieved was analyzed as a continuous variable. Linear regression analysis (stepwise regression) was used to screen independent related factors that may affect the number of oocytes retrieved, and the confounding factors identified in the single factor analysis were excluded. Regression coefficients (β values) and their 95% confidence intervals (CIs) were calculated. The size of the return effect was adjudged according to the absolute value of the standardized regression coefficient (β). Statistical tests were performed using a two-tailed alpha value of 0.05 with Bonferroni corrections (P<0.007 after the correction was considered to indicate a difference between groups). The statistical analyses were performed using SPSS version 24.0 (IBM Corporation, Armonk, NY, USA).