The patient is a 34-year-old woman with a body mass index (BMI) of 22 kg/m². Her menstrual cycle is usually 6–7 days every 27–28 days, with a moderate amount of bleeding and no dysmenorrhea. In January 2017, she underwent surgical treatment for intramural fibroids in our hospital. Hysteroscopy showed endometrial polypoid hyperplasia, and electroresection was performed. Laparotomy revealed extensive pelvic adhesions. Both fallopian tubes and ovaries were tightly adhered to the pelvic cavity. The fimbria of the right fallopian tube was atretic, and the left one was incompletely atretic with the disappearance of the fimbrial structure. Intraoperative hydrotubation showed that the left fallopian tube was poorly filled, and the right one was blocked. Therefore, myomectomy, pelvic adhesiolysis, and bilateral salpingectomy were performed.

In 1995, she underwent surgical repair for congenital heart disease (ventricular septal defect). In January 2017, echocardiography showed mild mitral and tricuspid regurgitation. She has a history of alcohol allergy. She had one induced abortion due to an unplanned pregnancy.

Physical and gynecological examinations were normal. Cervical cell and HPV tests showed no intraepithelial lesions or malignancies. Her chromosomal karyotype was 46, XX. In July 2017, the basic endocrine test showed: follicle stimulating hormone (FSH)/luteinizing hormone (LH) = 8.6/5.15, estradiol (E₂) < 20 ng/L, and CA125 = 16.1 U/ml.

The male partner of that woman is 43 years old with a BMI of 25.3 kg/m². He has normal erectile function, normal duration of sexual activity, and normal ejaculation function. In July 2017, the sperm analysis showed that the total sperm count (TSC) is 14 million/ml, progressive motility (PR) is 25%, and the normal morphology rate is 1%. The scrotal ultrasound showed no obvious abnormalities. There is no special information in his past medical history, personal history and reproductive history.

There is a family history of thalassemia. The male partner is diagnosed with male infertility, mild oligospermia, mild asthenospermia, and mild α-thalassemia. His chromosomal karyotype was 46, XY.

The long luteal phase protocol was adopted in the first cycle. Triptorelin (GnRHa, Dabijia, Huiling Company, 3.75 mg) at a dose of 1.25 mg was administered subcutaneously for down-regulation. Fourteen days later, recombinant human follicle-stimulating hormone (r-hFSH, Gonafen, Merck Serrano, 75 IU) was initiated at a subcutaneous injection dose of 150 U per day. After 3 days of administration, hormone levels were measured: E₂ was 82 pg/ml and LH was 1.14 mIU/ml. Considering the follicular development, the dose of r-hFSH was increased to 187.5 U per day for subcutaneous injection and administered for four consecutive days. Hormone levels were re-measured: E₂ increased to 738 pg/ml and LH decreased to 0.93 mIU/ml. Subsequently, the dose of r-hFSH was adjusted to 150 U per day for subcutaneous injection, and highly purified human menopausal gonadotropin (uHMG, HemeiQi, Huiling Company, 150 U) at a dose of 75 U per day was added for intramuscular injection. After 3 days of combined administration, hormone levels were re-checked: E₂ reached 3,131 pg/ml and LH was 1.55 mIU/ml. The administration of 150 U of r-hFSH subcutaneously and 75 U of uHMG intramuscularly was continued for one more day. Then, recombinant human chorionic gonadotropin (rHCG, Aize, Merck Serrano, 250 ug) at a dose of 250 μg was injected subcutaneously for triggering ovulation. Oocyte retrieval was performed 36 h after triggering under the monitoring of transvaginal ultrasound. In the fresh cycle, two cleavage-stage embryos were transferred, but early spontaneous abortion (7 weeks) occurred, and chorionic villus tissue testing was not performed.

Ultra-long GnRH agonist protocol was adopted in the second cycle 1 year later. Triptorelin (GnRHa, Dapagin, Yipu Sheng Company, 3.75 mg) is administered subcutaneously at a dose of 1.25 mg each time. A total of two down-regulation injections are given, with an interval of 15 days between the two administrations. Fourteen days after the last down-regulation, recombinant human follicle-stimulating hormone (r-hFSH, Pulikon, MSD, 300 IU) is used to initiate ovulation induction at a subcutaneous injection dose of 175 U per day for five consecutive days. At this time, the hormone levels are E₂ level of 495 pg/ml and LH level of 0.79 mIU/ml. The dosage of r-hFSH is reduced to 100 U per day for subcutaneous injection. Meanwhile, uHMG 75 U is added for intramuscular injection per day, and this regimen is used for 3 days. At this time, the hormone levels change to E₂ level of 3,937 pg/ml and LH level of 3.10 mIU/ml. Continue the subcutaneous injection of r-hFSH at 100 U and the intramuscular injection of uHMG at 75 U per day for one more day. Then, human chorionic gonadotropin (HCG, Zhuhai Lizhu Group, 2,000 U) at a dose of 10,000 U is administered intramuscularly for triggering. Oocyte retrieval is performed 36 h after triggering under the monitoring of transvaginal ultrasound. In the fresh cycle, two cleavage-stage embryos were transferred, but early spontaneous abortion (12 weeks) still occurred. The chorionic villus tissue test results showed: 45, X.

After 7 months, GnRH antagonist was adopted in the third cycle. Ovulation induction was initiated with subcutaneous injection of 200 U of r-hFSH per day for 5 days. After that, the hormone levels were measured, showing an E₂ level of 902 pg/ml and an LH level of 4.79 mIU/ml. The subcutaneous injection of 200 U of r-hFSH per day was continued. Additionally, gonadotropin-releasing hormone antagonist ganerik acetate (GnRH-A, Eucalyptus, Mercado, 0.25 mg) was subcutaneously injected at a dose of 0.25 mg per day for 3 days. Then, the hormone levels were re-measured, with an E₂ level of 2,688 pg/ml and an LH level of 2.26 mIU/ml. The subcutaneous injection of 200 U of r-hFSH per day was continued for one more day. Then, 10,000 U of HCG was intramuscularly injected, and 0.1 mg of triptorelin (GnRHa, Dafirin, Iproxen, 0.1 mg) was subcutaneously injected for triggering. Oocyte retrieval was performed under transvaginal ultrasound monitoring 36 h after triggering. In the fresh cycle, one cleavage-stage embryo was transferred, unfortunately, early spontaneous abortion recurred (9 weeks), and chorionic villus tissue testing was not performed.

Ovulation induction protocol was adopted in FET cycle 2 years later. Intramuscular injection of urinary gonadotropin (HMG, Zhuhai Lizhu Group, 75 IU) was used for ovulation induction treatment at a dosage of 75 U per day via intramuscular injection. After four consecutive days of initial administration, follicular monitoring was carried out, revealing that the largest follicle on the left side had a diameter of 8.5 mm, and the largest follicle on the right side also measured 8.5 mm in diameter. Based on these monitoring results, HMG treatment was continued for another 5 days. Subsequently, hormone level detection and follicular monitoring were performed. The hormone values were E₂ level of 244 pg/ml, LH level of 85.15 mIU/ml, and P level of 0.49 ng/ml. Follicular monitoring showed that the diameter of the largest follicle on the left side increased to 18.0 mm, while the largest follicle on the right side remained at 8.5 mm. Meanwhile, the thickness of the endometrium was 11.2 mm, with a classification of type A. One day after the above monitoring results, luteal support treatment was initiated, with a treatment cycle lasting for 17 days. The specific medication regimen was as follows: progesterone injection (Guangzhou Baiyunshan Mingxing, 20 mg) was administered at a dosage of 40 mg per day via intramuscular injection, dydrogesterone tablets (Dafu Tong, Abbott Laboratories, 10 mg) were taken orally at a dosage of 10 mg, with three times a day. On the sixth day after the start of luteal support treatment, a Day 6 frozen blastocyst that passed chromosomal screening and was deemed available was thawed and transferred. The woman attained a successful pregnancy and delivered a healthy infant in the FET cycle.

Accordingly, the scoring format was replaced with a numerical shorthand that sequentially represents cell number, stage-specific cell size, and fragmentation (4). For example, ″811″ was defined to embryos with 8 cells and symmetrical stage-specific cell size and less than 10% fragmentation. ″721″ was defined to embryos with 7 cells and unsymmetrical stage-specific cell size and less than 10% fragmentation.

Blastocysts morphology was evaluated according to the scoring system established by Gardner and Schoolcraft (5). Briefly, blastocysts were scored according to their expansive degree and hatching status, as below: (1), an early blastocyst with a blastocoels cavity which is less than half of the embryo volume; (2), a blastocyst with a blastocoels that is half of or larger than half of the embryo volume; (3), a blastocyst with a blastocoel that is full of the whole embryo; (4), an expanded blastocyst with a blastocoel filling the embryo and a thinning zona pellucida; (5), a hatching blastocyst with the trophectoderm beginning to extrude from the zona pellucida; and (6), a hatched blastocyst which has completely escaped from the zona pellucida. In addition, according to the development condition of inner cell mass and trophectoderm, the blastocysts graded as 3–6 was assessed as follows: for the inner cell mass: (A), numerous cells packed tightly; (B), several cells loosely grouped; or (C), only very few cells; for the trophectoderm: (A), large numbers of cells forming a cohesive epithelium; (B), few cells forming a loose epithelium; or (C), very few large cells.