Data from nearly 37,000 IVF cycles in the US between 2012 and 2015 showed that fresh eggs resulted in a slightly greater chance of a good birth outcome, which the researchers defined as a single, non-premature baby delivered at a healthy birth weight.
'Our study found that the odds of a good birth outcome were less with frozen than with fresh, but it was a small difference', says lead author Dr Jennifer Eaton, of Duke Fertility Centre in North Carolina.
When the quality of fertilised eggs and the age of both mother and donor were taken into account, the team found that fresh eggs led to good birth outcomes in 24 percent of cycles compared to 22 percent of the cycles with frozen eggs.
The rates of embryo implantation, pregnancy and live birth were all significantly higher among the women using fresh eggs compared to frozen, but fresh eggs also led to a 37 percent higher chance of multiple births, which could pose greater risk for both mothers and babies.
Donor eggs are often used for older women or women who have a decreased egg supply. This has led to an increased demand for frozen donor eggs which are a cheaper and faster option than fresh donor eggs. But it was previously unknown which type provides the best birth outcomes.
Although this study is the first to show an advantage of fresh donor eggs over frozen, the researchers say that doctors should take the other benefits of using frozen eggs into account when discussing the best option with patients.
'Given that frozen eggs have many benefits such as ease, cost, and speed, the decision to use fresh or frozen donor eggs should be made on an individual basis after consultation with a physician', said Dr Eaton.
The study was published in the journal Obstetrics and Gynaecology.