No blastocyst

In some IVF or ICSI cycles, eggs fertilise successfully but the resulting embryos stop developing before reaching the blastocyst stage, which is usually assessed on day five or six of laboratory culture. This outcome, sometimes described as embryos arresting in development, can happen even with good early embryo appearance and does not necessarily mean anything was done incorrectly in the laboratory. Reasons can include chromosomal abnormalities in the embryos, or other biological factors affecting egg or sperm quality that are not identifiable in advance. Because not every fertilised egg is expected to reach blastocyst stage, this outcome, while disappointing, is a recognised part of the natural attrition seen in embryo development, and does not mean a future cycle will have the same result. The clinical and embryology team will review the cycle with the patient and discuss whether any changes to future stimulation, laboratory approach, or additional testing may be relevant, along with the option of counselling support, which is generally available through the clinic.

Also known as: embryos stopped developing, no embryo reached blastocyst, embryo arrest

Last reviewed: 9 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.