Patients
This was a retrospective cohort study carried out at the Center for Reproductive Medicine and Infertility, The Fourth Hospital of Shijiazhuang, from March 2015 to May 2020. A total of 62 patients who had undergoing oocyte reception program were separated into two groups: Group I, PCOS oocyte receptors(n=30); Group II, non-PCOS receptors(n=32). PCOS patients were based on the Rotterdam criteria as having two or more of the following: (i) amenorrhoea or oligomenorrhoea (<10 menstrual cycles per year), (ii) clinical or biochemical hyperandrogenism, (iii) polycystic morphology on ultrasound, and excluding hyperandrogenaemia, such as congenital adrenal hyperplasia, hyperprolactinaemia, or androgen secreting neoplasia [8]. The receptor patients included in the analysis were <38 years at the oocyte reception, accepted fresh oocytes and were undergoing their first single vitrified-warmed blastocyst transfer (SVBT). Exclusion criteria donate freezen oocytes, or without single blastocyst transfer (Fig.1).
Institutional review board approval was obtained; hospital records of deliveries of all patients were reviewed. The Fourth Hospital of Shijiazhuang Ethics Committee approved this study.
Stimulation, Oocyte Retrieval, Fertilization, Embryo culture and Scoring
A detail of ovarian stimulation and oocyte retrieval has been previously described by Yan Jiang, et al. [9]. Health regulations permit oocyte donation only from IVF patients who have 20 or more mature oocytes retrieved from a single cycle, of which at least 15 must be kept for their own treatment [10]. So donate 6 oocyte every cycle.
Sperm used for either routine IVF insemination or ICSI procedure using a standard method. Insemination were performed at 38~40 h after trigger. Fertilization was identified by the presence of two pronuclei approximately 16-19 hours after insemination or microinjection. On day 3 embryos were transferred into G-2 culture medium in group culture (Vitrolife, Sweden). In the moring of D5 or D6 blastocysts were scored by two experienced embryologist using the system of Gardner and Schoolcraft [10].
Blastocyst vitrification and warming procedures
Embryos derived from donated oocytes must be cryopreserved and cannot be transferred to prospective recipients, until donors have been screened to be free of communicable diseases after 6 months [2,11]. The procedure was always performed using one blastocyst for each straw. An artificial shrinkage (AS), using a laser pulse was performed before vitrification. The blastocyst was then moved at room temperature (22–25°C) to Kitazato (Japan) equilibration solution (ES). After 6–8 min, the blastocyst was quickly washed in vitrification solution (VS) for 45–60s and transferred onto the straw (Kitazato Japan) using a micropipette and immersed vertically into liquid nitrogen [12].
An Kitazato (Japan) Thaw Kit was used for warming. The carrier containing the embryo was removed from the straw and placed quickly into the dish containing the thawing medium (thawing solution) preheated at 37°C. The blastocysts immediately fell from the device and could be easily identified in the medium. After 1 min, blastocysts were transferred to the DS medium (dilution solution) for 3 min at room temperature 22–25°C. In the last two step, blastocysts were placed for 5 min, in the WS1 medium and WS2 (washing solution). The embryo was then returned to G-2 medium for culture until transfer. At this stage, an assessment was performed on an inverted microscope to establish if the embryo survived based on morphological integrity of the ICM and trophectoderm. After 1 or 2 h of culture the embryo was reassessed again and often the re-expansion of the blastocoel was reported; this indicated that the embryo physiologically survived the warming procedure. Embryo transfer was normally performed within 2 or 3 h. All programmed warmed cycles, both at D5 and D6, were transferred in D5 endometrium [12].
Clinical outcome
Observation of the gestational sac and fetal heart by B ultrasound at 35 days after implantation was diagnosed as clinical pregnancy. The implantation rate was defined as the ratio between the number of gestational sacs and fetal heart observed under B ultrasound and the number of transferred blastocysts. Implantation rates, pregnancy rates, and multiple pregnancy rate of SVBT were analyzed.
perinatal and neonatal outcomes
Patients in both groups were given the same standard high-risk obstetric care under the care of the same group of obstetricians. Perinatology consultants were involved whenever there were additional high-risk factors such as Pregnancy-induced hypertension (PIH), gestational diabetes (GDM), or preterm birth (PTB; live birth before 37 weeks gestation).
PIH is defined as new onset of hypertension after the 20th week of gestation with or without proteinuria. GDM is defined as a glucose intolerance of varying severity with onset or first recognition during pregnancy [13].
Data Analysis
Statistical analyses were performed using SPSS 19.0 statistical software (SPSS Inc.). The results are presented as the mean±standard deviation (SD). The mean values of two groups were compared using the independent samples t-test. Percentages were compared using the χ2 test and P<0.05 was considered statistically significant.
