The effects of fresh embryo transfer and frozen-thawed embryo transfer on the perinatal outcomes of single fetuses from mothers with PCOS.

Polycystic ovary syndrome (PCOS) is the most common endocrine disease in women of childbearing age. PCOS is also a common cause of anovulatory infertility, accounting for approximately 80% of anovulatory infertility cases [ 1 , 2 ]. With the increasing number of infertile people, assisted reproductive technology represents a new treatment for people with infertility [ 3 ]. The most critical difference between fresh embryo transfer and frozen-thawed embryo transfer (FET) is the continuous change in the hormone environment after COH. Compared with women with normal ovulation, PCOS patients have a stronger ovarian response. The supraphysiological level of estradiol caused by ovarian stimulation can affect embryo implantation, placental development and blood supply, resulting in adverse outcomes [ 4 – 7 ]. However, FET technology can reduce the supraphysiological state after ovarian stimulation and provide a more favorable intrauterine environment for embryo implantation and placenta formation [ 8 ]. However, it is still unclear whether there are differences in perinatal outcomes between women who undergo fresh and frozen-thawed embryo transfer. Therefore, the purpose of this study was to explore and analyze the effects of fresh embryo transfer and frozen-thawed embryo transfer on the perinatal outcomes of singletons from mothers with PCOS.

Our retrospective study included 566 patients: 104 patients in Group A, 212 in Group B, 102 in Group C and 148 in Group D. The patient characteristics are presented in Table 1 . The BMI and bFSH and bLH levels in Groups A and C were higher than those in Groups B and D; the level of bE 2 in Group C was higher than that in Group B; The AFC of PCOS patients was higher than that of non-PCOS patients (P < 0.05). Compared with Group A * P < 0.05; compared with Group B ^ P < 0.05; compared with Group C # P < 0.05; compared with Group D † P < 0.05. (Indicates the statistical tests used to evaluate the differences between study groups). There was no significant difference in the total number of Gn days or endometrial thickness on the HCG test day among the groups (P>0.05). However, the E 2 level on the HCG test day, the number of retrieved oocytes and the number of high-quality embryos in the ET group were lower than those in the FET group. The number of IVF cycles in Groups B and D was higher than that in Groups A and C, whereas the opposite was true for ICSI cycles. Additionally, the number of cycles in Groups B and D was higher than that in Groups A and C. The number of day 3 embryos transferred in the ET group was significantly higher than that in the FET group, whereas the number of day 5 embryos transferred in the ET group was lower than that in the FET group (P<0.05) ( Table 2 ). Compared with Group A * P < 0.05; compared with Group B ^ P < 0.05; compared with Group C # P < 0.05; compared with Group D † P < 0.05. (indicates the statistical tests used to evaluate the differences between study groups). In this study, the clinical pregnancy rate of Group A was significantly greater than those of Groups B and D (P>0.05) ( Table 3 ). Compared with Group A * P < 0.05; compared with Group B ^ P < 0.05; compared with Group C # P < 0.05; compared with Group D † P < 0.05. (Indicates the statistical tests used to evaluate the differences between study groups). The perinatal data revealed 254 cycles of clinical pregnancy and delivery: 56 in Group A, 97 in Group B, 45 in Group C and 56 in Group D. The natural birth rate of Group D was significantly lower than that of Group A and Group B, and the cesarean section rate was significantly higher than that of group A and group B (P < 0.05) ( Table 4 ). Compared with Group A * P < 0.05; compared with Group B ^ P < 0.05; compared with Group C, # P < 0.05; compared with Group D, † P < 0.05. (Indicates the statistical tests used to evaluate the differences between study groups). A total of 157 pregnant women had clinical deliveries, 234 were followed up, and 11 were lost to follow-up. Among the pregnant women who were followed up, 50 were in group A, 88 were in group B, 42 were in group C, and 54 were in group D. The incidence of placenta previa in group B was significantly lower than that in group D, and the difference was statistically significant (P0.05) ( Table 5 ). Compared with Group A, * P < 0.05; compared with Group B, ^ P < 0.05; compared with Group C, # P < 0.05; compared with Group D † P < 0.05. (Indicates the statistical tests used to evaluate the differences between study groups). There was no significant difference in the incidence of neonatal hospitalization ≥ 3 d, neonatal hypoglycemia or perinatal death among the three groups (P > 0.05). However, in our study, the incidence of fetal distress in Group B was significantly lower than that in Groups C and D, the incidence of neonatal jaundice in Group D was significantly greater than that in Groups A and B, and the difference was significant (P < 0.05) ( Table 6 ). Compared with Group A * P < 0.05; compared with Group B ^ P < 0.05; compared with Group C # P < 0.05; compared with Group D † P < 0.05. (Indicates the statistical tests used to evaluate the differences between study groups). The results of univariate and multivariate analyses of possible factors affecting the clinical pregnancy rate of infertile patients are presented in Table 7 . According to the univariate analysis, bFSH, the number of oocytes retrieved, the number of high-quality embryos, the type of embryo transferred and PCOS were significantly correlated with the clinical pregnancy rate. After multivariate analysis, the number of high-quality embryos (OR = 1.119; 95% CI: 1.042–1.201; p = 0.002) was still independent factors associated with the clinical pregnancy rate ( Table 7 ). The possible factors affecting the clinical pregnancy rate of infertile patients were analyzed by univariate and multivariate analyses. In the single-factor analysis, the number of eggs obtained and the method of transplantation were significantly correlated with the low position of the placenta. After multivariate analysis, there was no significant correlation between the included indicators and the incidence of a low placenta ( Table 8 ). The possible factors affecting nonfetal distress were analyzed by univariate and multivariate analyses. According to the univariate analysis, there was a significant correlation between the embryo transfer method and the occurrence of fetal distress. In the univariate analysis, only the embryo transfer method was correlated. To reduce the deviation of the results, the indicators with P < 0.1 in the univariate analysis were included in the multivariate analysis. The embryo transfer method (OR = 0.030; 95% CI: 0.003–0.348; p = 0.005) was still a relevant factor for the incidence of fetal distress ( Table 9 ). The possible factors affecting the occurrence of neonatal jaundice were analyzed by univariate and multivariate analyses. In the univariate analysis, there was a significant correlation between the transplantation method, embryo transfer method and neonatal jaundice. After multivariate analysis, the transplantation method (OR = 0.219; 95% CI: 0.090–0.533; p = 0.001) was still an independent factor affecting the occurrence of neonatal jaundice ( Table 10 ).

In summary, young PCOS patients without risk of OHSS have a high clinical pregnancy rate with fresh transplant cycles. PCOS disease itself has no significant effect on the perinatal outcomes of the mother or singleton infant. Frozen-thawed embryo transfer may increase the incidence of low placenta, fetal distress and neonatal jaundice. Further attention needs to be given to the impact of embryo transfer methods on perinatal outcomes to optimize assisted reproductive technology, strengthen pregnancy management and screening, and ensure the health of mothers and children after assisted pregnancy. The advantages and disadvantages of fresh or frozen-thawed embryo transfer still need long-term exploration and research.

This was a retrospective analysis of patients who underwent IVF-ET-assisted conception at the Reproductive Center of the Affiliated Hospital of Guangdong Medical University between February 1, 2013, and March 27, 2021. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and national research committees and with the 1964 Helsinki declaration and its later amendments. This study was approved by the Ethics Committee of the Affiliated Hospital of Guangdong Medical University (PJKT2022-093). The study was initiated on 9/15/2022. Written informed consent was obtained from all patients, and all participants were informed that they could withdraw at any point during the study. The inclusion criteria for the PCOS group were as follows: (i) PCOS in accordance with the 2003 Rotterdam criteria; (ii) less than 35 years of age; (iii) retrieval of more than 5 eggs; (iv) selection of a long protocol; and (v) complete inspection index data in this center. The inclusion criteria for the control group were as follows: (i) less than 35 years of age; (ii) retrieval of more than 5 eggs; (iii) selection of a long protocol; (iv) infertility caused by tubal factors; and (v) complete inspection index data in this center. Patients were excluded from the study if they met any of the following criteria: (i) reproductive system abnormalities or chromosome abnormalities; (ii) twin or multiple pregnancy; (iii) severe mental, endocrine or systemic disease; (iv) myoma of the uterus, endometriosis or tubal factor disease; (v) premature ovarian failure or decreased ovarian function; (vi) a history of uterine surgery; or (vii) missing data or missing visits for external reasons. A total of 566 patients who met the inclusion criteria were included. Patients were divided into a fresh embryo transfer group and a frozen-thawed embryo transfer group according to whether fresh embryo transfer was performed. They were then divided into fresh embryo transfer and frozen-thawed embryo transfer groups. The patients were further classified into the ET-PCOS group (group A, n = 104), ET-non-PCOS group (group B, n = 212), FET-PCOS group (group C, n = 102), or FET-non-PCOS group (group D, n = 148). A long protocol for ovulation induction was used in the fresh cycle group. After the indicated standard was reached, 3.75 mg of long-acting GnRH-a (afolin, Huiling, Germany) was given on the 2nd—4th day of the menstrual cycle or mid-luteal phase, 0.8–1.875 mg GnRH-a was subcutaneously injected after ovulation on D7, or 0.05–0.1 mg GnRH-a was subcutaneously injected every day after ovulation on D7. When the pituitary downregulation standard [LH< 5 IU/L, E 2 < 50 pg/mL, endometrial thickness < 5 mm] was used, exogenous gonadotropin 75–225 U/d [Gonaven, Merck, Germany; Prikon, Mushadong, USA; or Lishenbao, Zhuhai Lizhu] was given for ovulation induction. When the diameter of at least one follicle was 19 mm, the diameter of two follicles was 18 mm, or the diameter of three follicles was 17 mm, the blood E 2 level reached 250–300 pg/mL for each dominant follicle (≥ 16 mm), or more than 60% for follicles greater than 16 mm, the injection of human chorionic gonadotropin (hCG) was 5000–10,000 IU that night. Fresh cleavage-stage embryos or blastocysts were transplanted on day 3 or 5 after fertilization. In the frozen-thawed cycle group, 2~3 thawed good-quality embryos were selected for resuscitation and transplantation. The following three transplantation protocols were applied. (1) The natural cycle is suitable for patients with normal ovulation and an endometrial thickness > 8 mm. The follicles and endometrium were monitored on the 10th day of menstruation, and follicles >16 mm in size were monitored daily until ovulation. After ovulation, 40 mg progesterone was given daily to promote endometrial progression to the secretory phase, and the embryo was thawed and transferred 3 days later. (2) Hormone replacement cycles are suitable for patients with irregular menstruation, ovulation disorders or previous monitoring of endometrial thinning. From the second to the third day of menstruation, 6–8 mg of estradiol valerate was orally administered daily, and the dosage was adjusted according to the patient’s condition. Endometrial thickness was monitored by B ultrasound after 10–12 days of treatment. If the endometrial thickness was < 8 mm, the dosage of estradiol valerate was increased orally, with a maximum of dose of 10 mg/d. When the endometrial thickness was ≥ 8 mm, a 100 mg/d progesterone needle was used to transform the endometrium, and resuscitation transplantation was performed 3 days later. (3) The ovulation cycle was deemed suitable for patients with a natural cycle endometrial thickness < 8 mm or menorrhagia. These patients were given 75 U of human menopausal gonadotropin (HMG) by intramuscular injection daily from the fifth day of menstruation and underwent B ultrasound monitoring of follicles and the endometrium after 5 days; the dosage was adjusted as needed. hCG (10,000 U) was given to induce ovulation when the dominant follicle diameter was ≥ 18 mm. After ovulation, 40 mg/d progesterone was given to prepare the endometrium for implantation, and 3 days later, the embryo was thawed and transplanted. After transplantation, progesterone (60–80 mg/d) was given. Serum hCG was detected 14–16 days after transplantation. Serum hCG > 5 U/L was positive. Twenty-eight days after transplantation, guided B ultrasound examination was performed to confirm the presence of an intrauterine pregnancy, and early cardiac motion indicated a clinical pregnancy. Follow-up of the pregnant women and their newborns was performed by telephone. This study was approved by the Ethics Committee of the Affiliated Hospital of Guangdong Medical University (PJKT2022-093). The conduct of this study is in line with the Declaration of Helsinki. SPSS 26.0 statistical software was used for data analysis. The adoption rate (%) of enumeration data indicates that the comparison of the rates between groups was performed via the χ2 test; normally distributed data are expressed as X ¯ ± SDs , the independent sample t test was used for comparisons, and the LSD t test was used for pairwise multiple comparisons. Nonnormally distributed data are presented as the median (quartile range) [M (P25–P75)], and the K‒W test was used for comparisons. The Mann–Whitney U test was used for comparisons between groups. When the number of events was less than 5, the chi-square test and Fisher’s exact test were used to analyze differences between groups, and P < 0.05 indicated that the difference was statistically significant.

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