Pregnancy - Fertilisation Of Eggs In Vitro

Test-tube babies is a misnomer: fertilisation takes place not in a test tube but in a petrie dish. This is one of the most skilled stages of IVF, conducted by a highly trained embryologist. The eggs and sperm are placed together in a special culture. Pre¬viously this was produced from a blood sample provided by the woman shortly before egg collection, but an artificial culture medium is now more frequently used. The petrie dishes are then kept at an even temperature in the laboratory. If fertilisation is going to take place, it will most likely be in the next 24 hours and sometimes the first signs may be visible after ten hours. The head of the sperm penetrates the outer layer of the egg, the zona pellucida, which then closes behind it. The nucleus of the sperm and the nucleus of the egg become visible under a microscope as two small circles within the egg, and then combine.

Sometimes fertilisation can be delayed, or the subdivision of the cells may take longer than usual. If nothing happens at all within the first 24 hours, then it might be possible for the man to provide a second sperm sample, for a further attempt at fertilisation. Although this can take place the second time around, and embryos can be transferred back into the woman, they are unlikely to be of very good quality. Carrying through with the procedure can be useful for diagnostic purposes, but is unlikely to result in a pregnancy.

There can be problems with fertilisation and a substantial number of women have the disappointment of going through all the drug taking and egg collection only to find that their eggs fail to fertilise. This can be due to a number of factors, including:
- prematurity or post-maturity of eggs;
- more than one sperm entering the egg;
- the egg containing more than one nucleus;
- gynogenesis or androgenesis, failure of either the male or female factor in the new embryo;
- the age of either the man or woman and the effects of this on the sperm or egg;
- poor culture or laboratory conditions.


Shirley M. Duran is a mother of two and an author of a variety of related lifestyle issues and topics with which has helped hundreds of mothers become pregnant. If you have any pregnancy questions for which you need answers, it is recommended to visit: http://mypregnancyquestions.info/

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