Influence of body mass index and self-administration of hCG on the outcome of IVF cycles: A prospective cohort study

Abstract

Final maturation of the oocyte in in vitro fertilization (IVF) cycles is achieved through the administration of a timed injection of human chorionic gonadotrophin (hCG). The success of mature oocyte retrieval is dependent on serum concentrations of the hormone reaching values capable of initiating meiosis and triggering the release of the cumulus-oocyte complex into the follicular fluid. The objective of this prospective cohort study was to examine the effect of adiposity, as measured by body mass index (BMI), on serum concentrations of hCG and gonadotrophins and to relate this to IVF outcome. A comparison was also made between professionally and non-professionally administered hCG to assess any possible effect on cycle parameters. A total of 50 patients with a high BMI (≥ 26 kg m^-2) who underwent IVF treatment at the Assisted Conception Unit, St James's University Hospital, Leeds, was recruited prospectively into the study. They were matched with 50 patients with a normal BMI (18–25 kg m^-2) who acted as a control group. The two groups were matched for age (mean of 32 years and range of 22–42 years) and cause of infertility. Serum gonadotrophins, oestradiol and hCG concentrations, measured at the time of oocyte retrieval, and the clinical outcome of the two groups were compared. Patients with a high BMI had a significantly lower mean serum hCG concentration compared with controls (63.9 versus 99.6 iu l^-1, P < 0.0003). They also required a higher dosage of gonadotrophin (3660 versus 3007 iu) to achieve follicular maturation than the controls. Similarly, the high BMI group of patients had higher serum concentrations of follicle-stimulating hormone (FSH) (12.3 versus 11.2 iu l^-1) and lower oestradiol (3499 versus 3506 pmol l^-1) compared with controls. Patients with a high BMI had significantly fewer oocytes aspirated, resulting in a significant decrease in the oocyte:follicle ratio compared with controls (33.9 versus 41.7, P < 0.05). The fertilization rate (46.2 versus 61.3%, P < 0.05) and clinical pregnancy rate per cycle (26.6 versus 37.1%, P < 0.05) were also lower in the patients with high BMI compared with those with normal BMI. The administration of hCG by the patient or her partner did not have a significant effect on clinical outcome. The mean serum hCG at the time of oocyte recovery was equivalent in both groups (87.1 versus 89.7 iu l^-1). Furthermore, the oocyte:follicle ratio (0.73 versus 0.72), fertilization rate (46.2 versus 54.2%) and clinical pregnancy rate (38.9 versus 36.5%) were similar. These findings indicate that high BMI is detrimental to the success of IVF treatment and has an important influence on the distribution and metabolism of hCG. The results also indicate that non-professional administration of hCG does not compromise cycle outcome.