Effect of intravenous anesthetic drugs on fertilization rate in oocyte retrieval.

We retrospectively analyzed the clinical data of subjects who received oocyte retrieval in the Affiliated Hospital of Nantong University from January 2020 to December 2021. The inclusion criteria were as follows: (1) infertile females who received oocyte retrieval in IVF treatment; (2) follow-up data were complete. The exclusion criteria were as follows: (1) the subjects presented comorbidities, including hypertension, diabetes, liver diseases, kidney diseases, thyroid illness and autoimmune diseases; (2) the subjects showed oocyte cryopreservation and no oocyte cycles; (3) the subjects had taken other therapies after IVF. The study complies with the ethical guidelines of the Declaration of Helsinki and was approved by the Institutional Review Board of Affiliated Hospital of Nantong University (No: 2019-K039), and informed consent was obtained from all subjects. The subjects were divided into the no-anesthesia group and the intravenous anesthesia group. In the no-anesthesia group, the oocyte retrieval was performed in the subject under a waking state. In the intravenous anesthesia group, the oocyte retrieval was performed in the subject falling asleep after anesthesia using intravenous propofol. Subject data including number of IVF cycles, ages of the couple, body mass index (BMI) of the female, duration of infertility, type of infertility (primary, secondary), infertility causes (tubal factor, ovulation disorders, endometriosis, premature ovarian insufficiency [POI], uterine factor, male factor, other causes and unexplained causes), ovarian stimulation protocols (A, B, C, D, E, F, G, H, I), basal follicle-stimulating hormone (FSH), basal luteinizing hormone (LH), basal estradiol (E2), basal antral follicle count (AFC), basal cancer antigen 125 (CA125), launch-day follicle-stimulating hormone (FSH), launch-day luteinizing hormone (LH), launch-day estradiol (E2), launch-day antral follicle count (AFC), trigger-day luteinizing hormone (LH), trigger-day estradiol (E2), trigger-day progesterone (P), the number of oocytes, the number of mature oocytes, fertilization way (IVF, intracytoplasmic Sperm Injection [ICSI], Half Intracytoplasmic Sperm Injection [HALF-ICSI]), anesthetic modality (no-anesthesia or intravenous anesthesia). The primary outcome was fertilization rate. In this study, fertilization rate was defined as the number of fertilized oocytes divided by the total number of retrieved oocytes. In our center, ovarian stimulation was performed based on the female’s age and ovarian reserve function. (A) The luteal phase long protocol: gonadotropin releasing hormone agonist (GnRH-a) was administrated in the luteal phase of the previous cycle; (B) The follicular phase long protocol: GnRH-a was administrated in the midluteal phase; (C) The ultra-long GnRH-a protocol: women received subcutaneous injections of long-acting GnRH-a for 2 to 4 months. (D) The ultra-short GnRH-a protocol: in this protocol, GnRH-a was used only once on day 2 of menstruation, after which gonadotropin (Gn) was initiated on day 3 and maintained until the administration of HCG. (E) The GnRH antagonist protocol: human menopausal gonadotropin (HMG) was administered daily from menstrual cycle day 3, and GnRH antagonist (0.25 mg/day) was added from stimulation day 6. (F) The progestin-primed ovarian stimulation (PPOS) protocol: hMG at 150–225 IU and medroxyprogesterone acetate (MPA) at 10 mg were administered daily from cycle day 3. (G) The micro-stimulation protocol: clomiphene was given orally from days 2 to 3 of the menstrual cycle. (H) The natural cycle protocol: no ovulation-inducing medication was given. (I) The other protocol: other methods for the treatment. Launch-day was defined as day 3–5 of a menstrual cycle, and trigger-day as the day of ovulation triggered with hCG or GnRH agonists. SPSS 25.0 statistical software was used for analysis. In the study, continuous variables were expressed as mean means ± standard deviation, and compared through Mann-Whitney U test. Categorized data were presented as rate (%), and compared through the Chi-square test. Poisson regression was used for multivariate analysis. A significant difference was considered at P  < 0.05. The two groups were balanced using PSM. We used 1:1 match on the nearest neighbor, and the caliper value was 0.05 (Fig.  1 ). A standardized difference of more than 0.1 indicated that the two groups were well balanced. Adjusted covariates in PSM included number of IVF cycles, ages of the couple, BMI of the female, duration of infertility, type of infertility, infertility diagnoses, ovarian stimulation protocols, basal FSH, basal LH, basal E2, basal AFC, basal CA125, launch-day FSH, launch-day LH, launch-day E2, launch-day AFC, trigger-day LH, trigger-day E2, trigger-day P, the number of oocytes, the number of mature oocytes, fertilization method, anesthetic modality. Fig. 1 Flow diagram Flow diagram

Before matching, statistically significant differences were found in the characteristics between the two groups, such as POI factor ( p  = 0.017) and male factor ( p  = 0.038). After matching, the baseline data between the two groups were not significantly different ( P  > 0.05). Before matching, the fertilization rate was 77% in the no-anesthesia group, and 76% in the intravenous anesthesia group, without significant between-group difference ( P  = 0.443). After matching, no difference was observed either ( P  = 0.685) (Table  1 ). Table 1 Comparison of clinical features before and after matching between the two groups case Variables Before matching After matching N0-anesthesia group( n  = 482) Intravenous anesthesia group( n  = 284) SMD P No-anesthesia group( n  = 258) Intravenous anesthesia group( n  = 258) SMD P Number of IVF cycles, mean (SD) 1.38 (0.69) 1.36 (0.70) -0.028 0.702 1.34 (0.67) 1.36 (0.68) 0.028 0.744 Female age, mean (SD), y 31.06 (4.67) 30.56 (4.64) -0.107 0.154 30.82 (4.43) 30.75 (4.73) -0.015 0.863 Female BMI, mean (SD), kg/m 2 23.13 (3.54) 23.15 (3.94) 0.005 0.946 23.13 (3.51) 23.26 (4.01) 0.033 0.693 Male age, mean (SD), y 32.06 (4.21) 31.54 (4.60) -0.113 0.112 31.77 (3.84) 31.74 (4.69) -0.005 0.951 Duration of infertility, mean (SD), y 3.20 (2.17) 3.07 (2.05) -0.066 0.399 3.25 (2.12) 3.11 (2.07) -0.070 0.440 Basal FSH, mean (SD), IU/L 7.75 (2.50) 7.46 (2.26) -0.126 0.116 7.59 (2.32) 7.54 (2.30) -0.022 0.805 Basal LH, mean (SD), IU/L 4.67 (2.50) 4.84 (2.76) 0.062 0.379 4.76 (2.62) 4.82 (2.75) 0.022 0.797 Basal E2, mean (SD), pg/ml 42.65 (19.16) 42.66 (22.05) 0.000 0.995 42.61 (19.84) 42.80 (21.99) 0.008 0.919 Basal AFC, mean (SD) 17.55 (11.95) 18.92 (12.47) 0.110 0.131 19.29 (12.32) 18.52 (12.17) -0.062 0.472 Basal CA125, mean (SD), U/ml 15.32 (6.81) 14.77 (6.64) -0.082 0.280 14.94 (6.63) 14.64 (6.62) -0.045 0.607 Launch-day FSH, mean (SD), IU/L 7.76 (2.64) 7.47 (2.49) -0.115 0.140 7.56 (2.56) 7.55 (2.52) -0.004 0.960 Launch-day LH, mean (SD), IU/L 4.61 (2.76) 4.67 (2.85) 0.020 0.784 4.60 (2.76) 4.69 (2.85) 0.031 0.723 Launch-day E2, mean (SD), pg/ml 46.87 (51.83) 44.66 (37.66) -0.059 0.496 47.09 (57.39) 44.71 (38.79) -0.063 0.583 Launch-day AFC, mean (SD) 14.15 (8.79) 15.04 (8.37) 0.107 0.168 14.86 (8.82) 14.94 (8.46) 0.009 0.919 Trigger-day LH, mean (SD), IU/L 3.81 (3.15) 3.65 (2.80) -0.059 0.455 3.62 (2.92) 3.75 (2.84) 0.047 0.603 Trigger-day E2, mean (SD), pg/ml 2451.88 (2197.88) 2769.22 (2413.64) 0.131 0.063 2700.69 (2396.70) 2642.27 (2278.14) -0.024 0.777 Trigger-day P, mean (SD), ng/ml 1.07 (0.63) 1.12 (0.69) 0.064 0.364 1.10 (0.62) 1.12 (0.71) 0.031 0.712 Number of follicles, mean (SD) 6.89 (4.39) 7.45 (4.71) 0.119 0.098 7.43 (4.51) 7.33 (4.72) -0.021 0.812 Number of mature follicles, mean (SD) 6.54 (4.29) 6.96 (4.47) 0.093 0.205 6.88 (4.42) 6.88 (4.53) 0.000 1.000 Type of infertility (n),% 0.842 0.655 Primary 291 (60.4) 168 (59.4) -0.021 148 (57.4) 154 (59.7) 0.047 Secondary 191 (39.6) 115 (40.6) 0.021 110 (42.6) 104 (40.3) -0.047 Infertility diagnoses Tubal factor (n),% 0.557 0.790 N0 286 (59.3) 161 (56.9) -0.049 149 (57.8) 145 (56.2) -0.031 Yes 196 (40.7) 122 (43.1) 0.049 109 (42.2) 113 (43.8) 0.031 Ovulation disorders (n),% 0.772 0.660 N0 398 (82.6) 230 (81.3) -0.033 204 (79.1) 209 (81.0) 0.050 Yes 84 (17.4) 53 (18.7) 0.033 54 (20.9) 49 (19.0) -0.050 Endometriosis (n),% 0.103 1.000 N0 475 (98.5) 273 (96.5) -0.113 253 (98.1) 254 (98.4) 0.021 Yes 7 (1.5) 10 (3.5) 0.113 5 (1.9) 4 (1.6) -0.021 POI (n),% 0.017 1.000 N0 391 (81.1) 249 (88.0) 0.211 224 (86.8) 225 (87.2) 0.012 Yes 91 (18.9) 34 (12.0) -0.211 34 (13.2) 33 (12.8) -0.012 Uterine factor (n),% 0.234 1.000 N0 473 (98.1) 273 (96.5) -0.090 251 (97.3) 252 (97.7) 0.021 Yes 9 (1.9) 10 (3.5) 0.090 7 (2.7) 6 (2.3) -0.021 Male factor (n),% 0.038 1.000 N0 376 (78.0) 201 (71.0) -0.154 187 (72.5) 188 (72.9) 0.009 Yes 106 (22.0) 82 (29.0) 0.154 71 (27.5) 70 (27.1) -0.009 Other causes (n),% 0.424 0.775 N0 422 (87.6) 254 (89.8) 0.073 232 (89.9) 229 (88.8) -0.038 Yes 60 (12.4) 29 (10.2) -0.073 26 (10.1) 29 (11.2) 0.038 Unexplained causes (n),% 0.096 0.515 N0 433 (89.8) 265 (93.6) 0.156 235 (91.1) 240 (93.0) 0.079 Yes 49 (10.2) 18 (6.4) -0.156 23 (8.9) 18 (7.0) -0.079 Ovarian stimulation protocols (n),% A(n),% 1.000 1.000 N0 481 (99.8) 283 (100.0) 0.057 258 (100.0) 258 (100.0) 0.000 Yes 1 (0.2) 0 (0.0) -0.057 0 (0.0) 0 (0.0) 0.000 B(n),% 1.000 0.866 N0 446 (92.5) 262 (92.6) 0.002 238 (92.2) 240 (93.0) 0.030 Yes 36 (7.5) 21 (7.4) -0.002 20 (7.8) 18 (7.0) -0.030 C(n),% 0.146 1.000 N0 481 (99.8) 280 (98.9) -0.083 257 (99.6) 258 (100.0) 0.038 Yes 1 (0.2) 3 (1.1) 0.083 1 (0.4) 0 (0.0) -0.038 D(n),% 0.070 1.000 N0 415 (86.1) 257 (90.8) 0.163 234 (90.7) 233 (90.3) -0.013 Yes 67 (13.9) 26 (9.2) -0.163 24 (9.3) 25 (9.7) 0.013 E(n),% 0.052 0.857 N0 220 (45.6) 108 (38.2) -0.154 102 (39.5) 99 (38.4) -0.024 Yes 262 (54.4) 175 (61.8) 0.154 156 (60.5) 159 (61.6) 0.024 F(n),% 0.923 0.886 N0 435 (90.2) 254 (89.8) -0.016 230 (89.1) 232 (89.9) 0.026 Yes 47 (9.8) 29 (10.2) 0.016 28 (10.9) 26 (10.1) -0.026 G(n),% 0.657 1.000 N0 478 (99.2) 282 (99.6) 0.080 257 (99.6) 257 (99.6) 0.000 Yes 4 (0.8) 1 (0.4) -0.080 1 (0.4) 1 (0.4) 0.000 H (n),% 0.217 1.000 N0 430 (89.2) 261 (92.2) 0.113 237 (91.9) 236 (91.5) -0.014 Yes 52 (10.8) 22 (7.8) -0.113 21 (8.1) 22 (8.5) 0.014 I(n),% 1.000 1.000 N0 470 (97.5) 276 (97.5) 0.001 251 (97.3) 251 (97.3) 0.000 Yes 12 (2.5) 7 (2.5) -0.001 7 (2.7) 7 (2.7) 0.000 Fertilization method(n),% 0.505 0.795 IVF 331 (68.7) 199 (70.3) 0.036 178 (69.0) 182 (70.5) 0.034 HALF-ICSI 42 (8.7) 18 (6.4) -0.096 15 (5.8) 17 (6.6) 0.032 ICSI 109 (22.6) 66 (23.3) 0.017 65 (25.2) 59 (22.9) -0.055 Fertilization rate 0.77 (0.27) 0.76 (0.26) -0.057 0.443 0.77 (0.27) 0.76 (0.26) -0.034 0.685 SD: standard deviation. SMD: standard mean difference. P : p -value Comparison of clinical features before and after matching between the two groups case SD: standard deviation. SMD: standard mean difference. P : p -value Before matching, Poisson regression analysis showed no effect of intravenous anesthetic drugs on fertilization rate (RR = 0.859, 95%CI:0.59 to 1.25, P  = 0.422) (Table  2 ). After matching, the effect of intravenous anesthetic drugs remained unobvious (RR = 0.935, 95%CI:0.67 to 1.29, P  = 0.681) (Table  2 ). According to the results of univariate analyses presented in Table  3 , variables including POI, ovarian stimulation protocols (C, E, and G), trigger-day E2, trigger-day P, number of mature follicles, fertilization method, and uterine factor were further examined in multivariable analyses, as shown in Table  4 . Statistically significant differences were observed in the impact of ovarian stimulation protocols (C) (b = 0.323, t = 2.421, p  = 0.016) and ovarian stimulation protocols (G) (b = 0.073, t = 2.028, p  = 0.043) on the fertilization rate, as well as in the impact of the number of mature follicles (b = 0.008, t = 2.380, p  = 0.018) and fertilization method (b = 0.063, t = 5.523, p  = 0.000) on the fertilization rate (Table  4 ). The administration of intravenous anesthesia drugs did not demonstrate a significant impact on the rate of fertilized eggs, as indicated by the statistical analysis (b = 0.017, t = 0.813, p  = 0.417) presented in Table  3 . Table 2 Results of the Poisson regression analysis Poisson regression analysis Before matching After matching RR (95%CI) P RR (95%CI) P Fertilization rate 0.859 (0.59 to 1.25) 0.422 0.935 (0.67 to 1.29) 0.681 Results of the Poisson regression analysis Table 3 Univariate analyses Variables b SE(b) t p Number of IVF cycles − 0.017 0.014 -1.164 0.245 Female age, mean − 0.002 0.002 -1.152 0.250 Female BMI − 0.004 0.003 -1.412 0.158 Male age 0.000 0.002 0.193 0.847 Duration of infertility − 0.005 0.005 -1.067 0.286 Basal FSH 0.003 0.004 0.730 0.466 Basal LH 0.002 0.004 0.562 0.574 Basal E2 0.000 0.000 − 0.433 0.665 Basal AFC 0.001 0.001 0.654 0.513 Basal CA125 − 0.003 0.001 -1.817 0.070 Launch-day FSH − 0.002 0.004 − 0.624 0.533 Launch-day LH 1.122E-5 0.004 0.003 0.997 Launch-day E2 9.928E-5 0.000 0.475 0.635 Launch-day AFC -5.738E-5 0.001 − 0.050 0.960 Trigger-day LH − 0.004 0.003 -1.306 0.192 Trigger-day E2 8.834E-6 0.000 2.055 0.040 Trigger-day P 0.036 0.015 2.430 0.015 Number of follicles 0.003 0.002 1.316 0.189 Number of mature follicles 0.008 0.002 3.470 0.001 Type of infertility − 0.004 0.020 − 0.198 0.843 Tubal factor 0.016 0.020 0.799 0.424 Ovulation disorders − 0.010 0.026 − 0.389 0.698 Endometriosis − 0.080 0.067 -1.198 0.231 POI − 0.054 0.026 -2.049 0.041 Uterine factor − 0.054 0.026 -2.049 0.041 Male factor 0.016 0.023 0.717 0.473 Other causes − 0.051 0.035 -1.479 0.140 Unexplained causes 0.010 0.031 0.318 0.751 Ovarian stimulation protocols (A) 0.235 0.272 0.861 0.389 Ovarian stimulation protocols (B) 0.011 0.037 0.289 0.773 Ovarian stimulation protocols (C) − 0.320 0.136 -2.356 0.019 Ovarian stimulation protocols (D) − 0.023 0.030 − 0.776 0.438 Ovarian stimulation protocols (E) 0.041 0.020 2.070 0.039 Ovarian stimulation protocols (F) 0.021 0.033 0.625 0.532 Ovarian stimulation protocols (G) − 0.102 0.033 -3.114 0.002 Ovarian stimulation protocols (H) 0.135 0.122 1.107 0.269 Ovarian stimulation protocols (I) − 0.052 0.063 − 0.821 0.412 Fertilization method 0.059 0.012 5.111 0.000 anesthesia − 0.017 0.020 − 0.813 0.417 Univariate analyses Table 4 Multivariable analyses Variables b SE(b) t p POI 0.004 0.030 0.118 0.906 Ovarian stimulation protocols (C) − 0.323 0.133 -2.421 0.016 Ovarian stimulation protocols (E) − 0.003 0.023 − 0.122 0.903 Ovarian stimulation protocols (G) − 0.073 0.036 -2.028 0.043 Trigger-day E2 -4.436E-6 0.000 − 0.754 0.451 Trigger-day P 0.022 0.017 1.309 0.191 Number of mature follicles 0.008 0.003 2.380 0.018 Fertilization method 0.063 0.011 5.523 0.000 Uterine factor − 0.032 0.024 -1.346 0.179 Multivariable analyses

Intravenous anesthetic drugs (propofol) might exert no obvious impact on the fertilization rate and pregnancy outcomes in subjects receiving IVF. This finding is worthy of large-size and multi-center studies in the future.

In clinical practice, an anesthetic modality should be set in subjects according to their willingness, pain tolerance, location of ovary and the number of oocytes. The current study showed that intravenous anesthetic drugs had no impact on the fertilization rate. Additionally considering that intravenous anesthesia could eliminate subjects’ pain and anxiety, related drugs might be recommended to females receiving oocyte retrieval in IVF. Previous studies have found that the fertilization rate is significantly associated with the pregnancy outcome [ 6 , 7 ]. The fertilization rate is a reliable biomarker of oocyte quality. There is also a strong relationship between the fertilization rate and the cumulative live birth rate (CLBR). Rehman et al.[ 8 ] have reported that subjects who have a lower fertilization rate achieve poorer pregnancy outcomes. Therefore, fertilization rate is used as a key laboratory indicator for the success or failure of IVF [ 9 ]. In this study, the intravenous propofol was used in the anesthesia group. As a popular intravenous drug, propofol functions fast, induces a smooth anesthesia, enables a rapid recovery, and minimizes postoperative events, such as nausea and vomiting. Propofol is also a lipid-soluble substance capable of entering the placenta. Anesthetic neurotoxicity in neonates and young children is a pressing concern [ 10 ] A large-scale retrospective study [ 11 ] in 2009 has found that children undergoing multiple exposures to anesthesia face an increased risk of neurocognitive defects. It reports that a single exposure to anesthesia before age 4 years is not associated with an increased risk of learning disability (LD), which may be observed in those with more exposures. Some studies [ 12 , 13 ] have reported that chronic and repeated exposure of sedation medication, including benzodiazepines, opioids, propofol, and ketamine, causes neurodegeneration, suggesting that exposures and outcomes may have a dose-response and temporal association. So, repeated and prolonged anesthetic exposure should be avoided in neonates and young children. The present study, for the first time, revealed that after the brief exposure to propofol at the oocyte stage, propofol did not affect the quality of embryos and the IVF pregnancy outcomes. Previous studies have investigated the effects of intravenous anaesthetics on pregnancy. In the studies by Ngamprasertwong et al.[ 14 ], an animal model of propofol-induced maternal fetal PK was successfully developed in pregnant sheep for the first time. The concentration of propofol in the fetus was much lower than that in ewes at mid-gestation. A study in the Europe has been conducted to investigate the anesthetics on learning at school age, finding that a brief duration of exposure is not associated with neurodevelopmental disabilities [ 15 , 16 ]. Another study has verified that the safety of intravenous anesthetic drugs in cesarean section, suggesting that propofol has no effect on fetal growth and development [ 17 ]. Two meta-analyses [ 18 , 19 ] have reported intravenous anesthetics, including propofol, fentanyl, and lidocaine, do not affect reproductive outcomes. Indirectly, these observations corroborate the conclusion of the present study. Notably, oocyte retrieval is anxiety-provoking in the IVF treatment [ 20 ]. It may take multiple attempts to obtain a pregnancy. Severe pain may cause problems, such as prolonged operation, premature termination, and side effects during surgical procedures. These unpleasant experiences could results in excessive worry about IVF treatment [ 21 ] A research of Yoon Frederiksenet al. [ 22 ] has shown that about 7% of women feel distressed during oocyte retrieval. Combined with the findings in the present study, anesthetic measures should and could be taken to relieve the pain in women receiving oocyte retrieval. The innovation of this study is that it adopts PSM to explore the effect of intravenous anesthetic drugs on fertilization rate for the first time. PSM can reduce inter-group differences and balance inter-group confounders. Meanwhile, there are some limitations to the study. First, this study is a single-center retrospective study with a small sample size, which may result in some deviations in the results. Even though PSM was used, unknown residual confounders could not be completely excluded.

Transvaginal ultrasound-guided oocyte retrieval, a standard but invasive procedure in in vitro fertilization and embryo transfer (IVF-ET), can be performed to obtain viable oocytes from ovarian follicles before ovulation through needle retrieval [ 1 ]. As the needle punctures through the vaginal wall and explores the eggs in the ovary, the subjects experience pain, which can be relieved by antiesthetic drugs [ 2 ]. However, it is unknown whether intravenous anesthetic drugs affect the fertilization rate and the in vitro fertilization (IVF) outcomes. During states of general anesthesia, the administration of propofol has been observed to decrease perfusion pressure in both follicles and the endometrium, as well as reduce hemoglobin concentration and plasma cortisol levels. The hemodynamic and biochemical alterations that occur following propofol infusion may have indirect implications for pregnancy outcomes. Propofol, known for its high lipophilicity, exhibited a direct relationship between the cumulative dose of propofol administered and the progressive accumulation of its concentrations in follicular fluid. The accumulation of propofol in follicular fluid has the potential to impact oocyte fertilization and subsequently influence the quality of embryos. Previous animal studies [ 3 , 4 ] have indicated that propofol may have an impact on early embryonic development, although limited human studies [ 5 ] have been conducted. In light of these findings, we sought to investigate the potential effects of propofol exposure during pregnancy. Therefore, we designed this retrospective cohort study involving subjects matched through PSM. This study attempts to explore the potential effects of intravenous anesthetic drugs on the IVF outcomes of subjects.

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