Pregnancy rate in IVF patients with unexpected poor response to ovarian stimulation.

ABSTRACT

OBJECTIVE: To evaluate whether an unexpected poor response (cases with ≤3 oocytes) leads to a reduction in the pregnancy rate in IVF cycles compared to a suboptimal response (controls with 4-9 oocytes) in women with adequate ovarian reserve. METHODS: A nested case-control study performed in a retrospective cohort of couples undergoing IVF at the Infertility Unit of the ASST Lariana. Cases and controls had adequate ovarian reserve and were matched 11 for female age and number of previous cycles. Cumulative clinical pregnancy rate per oocyte retrieval was the main outcome. RESULTS: Overall, 113 cases and 113 matched controls were included; the median number of available oocytes was 2 and 6, respectively. The cumulative pregnancy rate per cycle was significantly reduced in cases compared to controls with a crude odds ratio = 0.45 [95% Confidence Interval 0.28-0.82]. A binomial logistic model indicated that an increase in one oocyte increases the odds for cumulative pregnancy rate per cycle by 1.27 in women with 9 oocytes or less. The cumulative pregnancy rates per cycle in cases and controls, according to female age were respectively 29% versus 54% in patients aged <35 years (p = 0.036); 22% versus 43% in patients aged 36-39 years (p = 0.048) and 11% versus 13% in patients 40-45 years old (p = 0.72). Patients belonging to older age groups showed decreasing probability of cumulative clinical pregnancy rates both among cases and controls group (p < 0.05). CONCLUSIONS: The number of available oocytes significantly affects the probability of success in IVF cycles with unexpected impaired ovarian response.