population
The subjects are those patients who have undergone IVF-ET assisted fertility treatment at the Reproductive Center of Northwest Women and Children's Hospital from 2015.01.01 to 2019.06.01. They were selected according to the following criteria: (1) they were at their first fresh oocyte retrieval cycle; (2)their menstrual period is regular; (3) the number of oocytes harvested ≥ 4; (4) both couples are within the age of 22 to 36; (4) the causes of infertility are pelvic tubal disease and endometriosis; (4) both spouses have normal chromosomes; (5) in the past three months, no reproductive infections such as mycoplasma, chlamydia and gonorrhoeae had occurred. The subjects should also had no following conditions: (1) polycystic ovary syndrome (PCOS); (2) hyperprolactinemia; (3) diabetes and other diseases that may affect the test tube outcome. According to the obesity and overweight standards by the Chinese Obesity Working Group, they were divided into 4 groups: Group 1 (n = 3413, male and female BMI: 18.5≤BMI <24kg/m2), Group 2 (n = 1437, Female BMI≥24 kg/m2 and male BMI18.5≤BMI<24 kg/m2), Group 3 (n = 4283, female BMI18.5≤BMI<24 kg/m2 and male BMI≥24 kg /m2) and Group 4 (n = 2176, female BMI ≥ 24 kg/m2 and male BMI ≥ 24 kg/m2)(Figure1).
Research method
The doctor used gonadotropin to enhance releasing hormone (GnRH) agonist long protocol and antagonist protocol to promote ovulation. The subjects with normal or high-response ovarian response adopted the GnRH agonist long protocol, starting from the mid-luteal phase, subcutaneously inject triptorelin (Ferring GmbH , Germany) 0.1 mg/d for 14 days. Gonadotropin(Gn) was injected after reaching the downregulating standard(Follicle-stimulating hormone(FSH)<5U/L, Luteinizing hormone(LH)< After 5U/L, Estradiol(E2)<183pmol/L). The antagonist protocol was given Gn hyperstimulation from the 2nd to 3rd day of the menstrual cycle. From 5 to 6 days of hyperstimulation, cetrorelix acetate (Bayer, Germany) was injected subcutaneously at 0.25 mg/d to the day of human chorionic gonadotropin (HCG). When the diameter of more than 3 follicles is ≥18mm, HCG (Zhuhai Livzon, China) 5000~10000u was injected, and the oocytes were collected under the guidance of B ultrasound about 36 hours after the injection, and routine IVF treatment was performed 4 hours later. After fertilization, they were cultured in vitro for 72 to 120 hours, and at day 3, embryos or blastocysts were transferred. From the day of embryo/blastocyst transfer, 60 mg progesterone injection (Zhejiang Xianju, China) was intramuscularly injected daily to 70 days after clinical pregnancy. A biochemical pregnancy is a biochemical pregnancy if the blood HCG is detected 12 to 14 days after the transplantation, and a clinical pregnancy is a clinical pregnancy if the gestational sac and fetal heart beat are observed by B ultrasound 4 to 6 weeks after transplantation.
Evaluation standard of embryo and blastocyst
Embryo grading. Grade I: The size of the blastomere is uniform without fragments; Grade II: The size of the blastomeres is uniform or slightly uneven, fragments <20%; Grade III: The size of the blastomeres is uniform or mildly uneven, fragments 20-50%; Grade IV: The size of the blastomeres is uneven, and the fragments are more than 50%. Grade I~II are high-quality embryos, and Grade I~III are transferable embryos.
Blastocysts were graded according to Gardner and Schoolcraft (1999). The blastocysts were classified into 1 to 6 grades according to the degree of expansion and hatching of the blastocysts. Then, according to the number of cells and the degree of cell adhesion, the inner cell mass and trophoblast cells were divided into Grades A to C. Blastocysts with scores ≥3AA, 3AB, 3BA, 3BB on day 5, or blastocysts with scores ≥4AA, 4AB, 4BA, 4BB on day 6 to 7 are considered high-quality embryos.
Laboratory analysis
All serum was separated by centrifugation at 3500 rpm for 5 minutes and kept at room temperature for 1 hour. The levels of FSH, LH, P and TES were measured by chemiluminescence microparticle immunoassay (Beckman DXI 800, USA).
Statistical analysis
Descriptive statistics are presented as mean and standard deviation (SD). Continuous and categorical variables were compared between BMI groups using linear regression and group 1 as referent. Linear regression model was employed to assess the associations of BMI status and individual available embryo rate, high quality embryo rate, fertilization rate and cleavage rate by calculating b-coefficient and 95% confidence interval (CI). Odds ratio (OR) and 95%CI were calculated using multivariate logistic regression model. Model 1 adjusted male and female age. Model 2 adjusted for female age, male age, year of infertility, E2 on HCG day, FSH on HCG day, P on HCG day, LH on HCG day, number of available embryos, left testicular volume, and right testicular volume. Two sides P values less than 0.05 were considered significant. All analyses were conducted using Stata/SE 16.1.