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.