P–276 Factors associated with first oocyte retrievals affecting time to live birth – a retrospective study
Authors: Marques M , Rodrigues P , Aibar J , Carvalho M J , Plancha C E 
Published: August 2021

Abstract

Study question
Which are the main factors on first oocyte retrievals influencing the time to achieve a live birth?

Summary answer
The number of oocytes collected on the first retrieval is the most important factor to decrease time to live birth.

What is known already
The goal of infertile couples when they attend a fertility clinic is to obtain a healthy baby as soon as possible. Cumulative live birth rate is today considered the most reliable estimate of ART success. However, the time used to achieve such goal is still not clear both to health professionals and patients. Although there is a general idea of which factors predict ART success, both clinicians and embryologists are still not aware of which variables can effectively influence the time to a live birth.

Study design, size, duration
We analyzed retrospectively 333 couples who performed their first fresh IVF/ICSI cycles from January 2015 to December 2018, along with their eventual subsequent FET and/or IVF/ICSI cycles, leading to 146 live births. The aim of this study was to use “Time” as an additional measure of ART success, and to identify which variable of the first oocyte retrieval has a major influence on time to live birth.

Participants/materials, setting, methods
We included in total 430 oocyte retrievals and 147 FET cycles. Oocyte donation cycles were excluded. Data were studied cumulatively until the childbirth (couples at risk) or until the last treatment record (censored couples). Cox Regression Model for survival analysis was used to study the variables that may influence the time to live birth, in order to take both confounding and collinearity into account.

Main results and the role of chance
We considered the date of the first oocyte retrieval as the starting point and the date of the first childbirth as the ending point to determine the time to live birth. The mean age of the woman at the first oocyte retrieval was 36.8±4.67, the cumulative pregnancy rate 43.5% (95%CI:41.77%;45.23%) and the live birth rate 34.0%(95%CI:32.32%;35.63%).
As variables for the Cox Regression Model we selected the woman’s age and number of collected oocytes from the first oocyte retrieval. We also considered the number of frozen embryo transfers (FET).
We have found a positive association between the number of oocytes collected at the first oocyte retrieval and the period until obtaining a healthy singleton (HR = 1.20;95%CI:1.105–1.297;p&gt;0.001). Conversely, a negative association concerning the number of FET and time to live birth (HR = 0.32;95%CI:0.18–0.562;p&gt;0.001) was demonstrated. Importantly, woman’s age, was not found to have a significant effect on time to live birth.
Our results indicated that the number of oocytes collected at the first cycle, but not woman’s age, mostly affect time to live birth. Poor prognosis patients were found to be associated with several embryo transfers.

Limitations, reasons for caution
This is a retrospective study with a small number of cycles and freeze-all procedures were not included. Additional inclusion of freeze-all procedures in a larger study will be needed to confirm our preliminary results.
Wider implications of the findings: This study identified oocyte number at first collection as a major influence on time to live birth. Increased attention to the “Time” parameter will be helpful for health professionals and patients, to further personalize reproductive treatment procedures, potentially decreasing psychological burdens associated with ART treatments.

Trial registration number
Not applicable