Introduction Exogenous FSH administration to achieve supraphysiologic serum levels for multifollicular recruitment is a mainstay of modern invitro fertilization (IVF). Initial dosing and subsequent titration of these medications to optimize ovarian response is one of the most onerous and expensive parts of IVF for both the patient and the physician. Yet, it is still considered part of the art of assisted reproductive technology (ART), meaning there are no definitive data or clear guidelines on how to dose and titrate these medications. In addition, patient response to these medications can be unpredictable. While there are some data on excessive use of gonadotropins and detrimental Exogenous FSH is the catalyst controlling controlled ovarian stimulation (COS), with high dosing being associated with negative outcomes. A retrospective cohort study of COS cycles was performed to determine the effect dosing and BMI has on serum FSH levels and to determine if serum FSH levels are associated with changes in live birth rates. In this study, 397 GnRH suppressive cycles were analyzed. Serum FSH levels were measured every 48-72 hours throughout COS and the change (delta) in serum FSH levels from baseline was calculated. Elevated day 3 serum FSH levels were significantly associated with decreased live births (OR: 0.86; 95%CI: 0.78 0.94, p = 0.002), while antral follicle count (OR: 01.077; 95%CI: 1.028 1.128, p = 0.002), number of oocytes retrieved (OR: 1.053; 95%CI: 1.002 1.107, p = 0.04), and number of embryos transferred (OR: 1.292; 95%CI: 1.284 1.301, p < 0.001) were significantly associated with an increased birth rate. Elevated delta FSH and maximum serum FSH significantly (p < 0.001) correlated with a decrease in live births. Increased BMI significantly reduced serum FSH levels, suggesting BMI should be considered when calculating FSH dose. Overall, maximum serum FSH and elevated serum delta FSH levels were associated with lower live birth rates supporting a rationale for measuring serum FSH during COS.