Increased odds of live birth in fresh in vitro fertilization cycles with shorter ovarian stimulation.

OBJECTIVE: To investigate the impact of prolonged ovarian stimulation on pregnancy outcomes in IVF cycles with fresh day 3 ET.

DESIGN: Retrospective cohort study.

SETTING: University-affiliated center.

PATIENT(S): All patients initiating their first IVF cycle with fresh day 3 ET. Prolonged ovarian stimulation was defined as a duration of more than two standard deviations (95th percentile) for the study cohort (i.e., >13 days).

INTERVENTION(S): None.

MAIN OUTCOME MEASURE(S): Live birth rate was considered the primary outcome and was compared between patients undergoing ovarian stimulation for ≤13 days and >13 days. Odds ratios (OR) with 95% confidence intervals (CI) for all pregnancy outcomes after day 3 ET were calculated. The OR for live birth was adjusted using logistic regression.

RESULT(S): A total of 6,410 and 339 patients underwent ovarian stimulation for ≤13 days and >13 days, respectively. There were no differences in the demographics or mean number of day 3 embryos transferred between the two groups. Ovarian stimulation ≤13 days was associated with increased odds of clinical pregnancy (OR 2.15, 95% CI 1.19-3.89) and live birth (OR 2.35, 95% CI 1.25-4.43). The increased odds for live birth in the ≤13-day group remained unchanged after logistic regression. Patients with clinical pregnancies in the >13-day group were younger (34.6 ± 4.91 years) compared with those who did not conceive (38.2 ± 4.72 years).

CONCLUSION(S): Our findings suggest that ovarian stimulation ≤13 days is associated with increased odds of clinical pregnancy and live birth. In patients undergoing ovarian stimulation >13 days, younger age is associated with live birth.