Parameters for ovarian response
The patients were further divided into two subgroups based on the cut-off age of 38 years. Comparisons of the parameters for ovarian response between the two different BMI categories are presented in Table 2 and Table S1. Younger women (< 38y) with high BMI received a significantly higher dose of Gn stimulation (29 vs 26, z = 10.255, p < 0.001) and had a slightly longer duration of Gn stimulation (10 vs 10, z = 1.975, p = 0.048) than those with normal BMI (Table 2). There were more retrieved oocytes (14 vs 13, z = -3.312, p = 0.001), metaphase II oocytes (12 vs 12, z = -3.322, p = 0.001), normally fertilized oocytes (8 vs 8, z = -3.324, p = 0.001), cleavage (10 vs 9, z = -3.816, p < 0.001), cleavage-stage embryos (8 vs 8, z = -2.978, p = 0.003), and blastocyst (4 vs 4, z = -2.621, p = 0.009) in the normal BMI group than in the high BMI group. However, in the older women (≥ 38y) subgroup, compared to the normal BMI group, the duration of Gn stimulation was shorter (10 vs 10, z = -2.802, p = 0.005), and the cleavage was lower (7 vs 7, z = -2.141, p = 0.032) in the high BMI group. In both age subgroups, serum peak estradiol and progesterone concentrations on hCG day in the normal BMI group were significantly higher than in the high BMI group. No significant differences in the numbers of HQE and TQE were observed between the two BMI groups (Table 2 and Table S1).
Pregnancy outcome measures
As indicated in Table 3, the CLBR and cancellation rate showed a statistically significant reduction in younger women with high BMI compared to those with normal BMI (73.7% vs 76.8%, p = 0.008; 28.6 % vs 34.8%, p < 0.001, respectively), but no significant differences were observed in the older women subgroup (Table S2).
Other pregnancy outcomes are presented in Table 3 and Table S2. There were no significant differences in implantation rate, CPR, OPR, LBR, ectopic pregnancy rate, biochemical pregnancy rate, ESAR, and LSAR for all age subgroups between the two BMI groups. No significant differences were found in the rates of singleton pregnancy and multiple pregnancy.