Research QuestionDoes very advanced maternal age (VAMA, aged 45+) influence obstetric outcomes among women using donor oocytes in in vitro fertilization (IVF)? DesignThis retrospective cohort study analysed data from a nationwide IVF registry in Taiwan, focusing on IVF cycles involving women aged 45 or older using donated oocytes between 2007 and 2016. The study assessed cumulative live birth rates (CLBR) and secondary outcomes such as clinical pregnancy, miscarriage, live birth, and twin pregnancy rates, alongside perinatal outcomes like caesarean section rates, preeclampsia, gestational diabetes, and birth weight. ResultsThe study included 1,718 embryo transfer cycles from 745 women, with a stable live birth rate of about 40% across the study period. The CLBR was slightly lower in women over 50 (54.2%) compared to those aged 45-46 (58.0%), but these differences were not statistically significant (p=0.647). Secondary outcomes and perinatal outcomes did not significantly differ across age groups. Regression analysis suggested a non-significant decrease in live birth rates and birth weight with increasing maternal age. The study also found that single embryo transfer (SET) minimized the risk of twin pregnancies without significantly affecting live birth rates. ConclusionsIVF with donor oocytes remains a viable option for women of VAMA, with consistent live birth rates across age groups. However, the study underscores the importance of elective SET to reduce the risk of twin pregnancies and associated adverse outcomes. Further research is needed to explore the impact of other factors such as paternal age and embryo development stage on IVF success in this population.