A new study has come to the conclusion that infertile women who are seeking to undergo in vitro fertilization (IVF) may have a bit of a problem — at least when it comes to frozen donor eggs.

There is a rising use of frozen eggs, which are much more convenient and easier to have in stock than fresh eggs, and some IVF centers have even established donor egg banks dedicated to frozen eggs, according to a CBS News report.

However, a new study by researchers at the Center for Human Reproduction in New York City finds that frozen eggs offer a lower chance of pregnancy and delivery than fresh eggs after IVF. It’s something patients should be aware of before they opt to choose frozen over fresh eggs.

Fresh eggs were typically used for certain IVF procedures, when they are fertilized iwth partner sperm and then transferred into a woman’s uterus. But because of the requirement of keeping fresh eggs, women sometimes had to wait months. Frozen eggs, meanwhile, can be kept on hand until someone needs them. This gives women a wider field of access to donors, allowing much better flexibility and coordination.

However, it comes with a lower success rate, this study finds.

Still, women may find the flexibility and convenience to be preferable to waiting months for fresh eggs, even though it has a slightly higher success rate.

The study was published in the Journal of the American Medical Association and it examined 11,000 IVF procedures using donor eggs in 2013. About 20 percent of them involved frozen eggs. Live births turned out significantly better for those who used fresh eggs, with a live birth rate of 56 percent compared to 47 percent for frozen eggs.