18 hours after fertilisationIn the morning at 8 o’clock (18 hours after fertilisation), the oocytes are examined again to see if fertilisation has taken place correctly. The oocytes are checked for pronuclei. One pronucleus comes from the oocyte, the other from the sperm. If fertilisation takes place correctly, one can see two pronuclei in the morning after oocyte collection (arrow). Furthermore the embryologist looks at whether there are two polar bodies present and at the thickness of the zona pellucida (* in the picture).The embryoscopeAll oocytes are continuously monitored every 10 minutes in our embryoscopes, two brand new high-tech incubators that monitor embryo development continuously with an infrared camera. Although it is possible to describe embryo development and embryo-quality with letter codes, a short time-lapse film tells much more about embryo-quality than you can write down on a table.New research has shown that the early cleavages of the human embryo are essential for human embryo development. This enables us to detect inborn errors in the first cleavages that reduce the potential of the single embryo to give rise to a healthy offspring.26 hours after fertilisationIn the afternoon at 14:00 (26 hours after fertilisation) the embryologist checks whether the oocytes have cleaved for the first time. Has the first cleavage taken place at that time it is noted as early cleavage, which is a good sign, unless it takes place too early. Embryos with early cleavage are also investigated for presence of nuclei within the cells, and whether the size of the cells is equal.The monitoring of all embryos takes place continuously in the embryoscope, so we constantly can see how development is progressing without removing the embryos from the incubator.