What happens in the IVF lab? The theory After the ovarian puncture, the vials in which the egg cells are kept are immediately sent to the lab and the highly mobile sperm cells are added to them. The egg cells, together with the sperm cells, are placed in an incubator at body temperature and at a set relative humidity and C02 concentration (Figs. 5a, 5b and 6). One day later, the cells can be examined microscopically to determine whether or not they have been fertilized. Fertilization is the fusion of a sperm cell with an egg cell. At that point, a fertilized egg cell has not yet divided but contains two pronuclei, which are visible under the microscope (Fig. 7). Each pronucleus contains the genetic material of the woman or the man. The embryo transfer occurs either on day 3 or on day 5 after the ovarian puncture. On day 3, the embryos are in the 8-cell stage. On day 5, the embryo is called a blastocyst (a group of approximately 50 cells surrounding a cavity). The day is chosen in consultation with the doctor and the embryologist. Sometime the decision is made the day after the ovarian puncture and sometimes only after day 3 (Figs. 8 and 9). The goal is to determine the optimal moment, regardless of the number of embryos and their quality, for selecting the best embryos to be transferred. Before the transfer, the quality of each embryo is evaluated using a point system. The quality of the embryo is determined by the uniformity and integrity of the individual cells. Some cells become fragmented because cellular material is expelled during cell division (Figs. 8 and 9). The more fragmentation that occurs, the smaller the chances of implantation (= pregnancy). When pregnancy is achieved after the implantation of less than ideal embryos, the result of the pregnancy and the health of the child are as just as good as after the implantation of a 'perfect' embryo. The quality of the embryo is therefore not related to whether or not the child that is produced is normal.
Fig. 5a: Incubator where the embryos develop
Fertility Centre
Fig. 5b: Embryo culture dish
In practical terms The day after the ovarian puncture, the IVF laboratory will contact you to tell you the result of the fertilization procedure (the number of embryos) and to make an appointment for the actual embryo transfer. For more information about the actual embryo transfer, please see below.
21