Beginners' guide to genetics: congenital malformations
In the fourth part of our series, Adrián J González and colleagues describe how congenitial malformations occur
Not everything can be explained only on the basis of genetics. At certain times during intrauterine life, the fetus is susceptible to different elements, that affect future development.
During the first week after fertilisation, cell division and implantation occur and are vital for future development. It is estimated that between one half and two thirds of all human conceptions do not develop successfully to term. Many of these embryos express their abnormality so early that they fail to implant in the uterus. Others implant but fail to establish a successful pregnancy. Indeed most abnormal embryos are spontaneously aborted, often before the woman even knows that she is pregnant.1 Chromosomal errors can be found in more than two thirds of these early abortions.
Genetic events can result in congenital malformations in very early development stages. These congenital malformations are caused by gene mutations and chromosomal structural or numerical anomalies--for example, aniridia,