Congenital Malformations

Introduction

Congenital malformations are diseases characterized by structural deformities which are caused by problems in the development of fetus before birth. These conditions are existing at birth and often before the birth regardless of their causation.

Nowadays, there are various methods available for early detection of chromosomal and other genetic abnormalities in the fetus during pregnancy itself. These methods are amniocentesis, chorionic villus sampling, and other newer diagnostic tests. The number of babies born without detection of congenital problems is reducing day by day. However, there still are some unfortunate newborns born with abnormal look, development and function which usually affect their entire lives.

Types of congenital malformations

The congenital malformations can be divided into five categories depending on their cause as follows:

1) Chromosome Abnormalities:

Chromosomes are microscopic structures in the cells which carry the genetic material from one generation to the next. In a normal fetus, twenty-three chromosomes come from the father and twenty-three from the mother, and all are found in the center of every cell in the body except the red blood cells. The genes carried on the chromosomes determine the growth of the baby, her looks and to some extent her behavior.

Some medications taken during pregnancy are toxic and can cause permanent damage to the fetus such as thalidomide.

In some situations, the child does not have the normal forty-six chromosomes, or some parts of chromosome is missing or duplicated, or there is transfer of a piece of one chromosome to other. In such cases the baby may abnormal or behave differently from other children of her age, and she can develop serious health problems. Down syndrome is an example of a condition that can occur when a child is born with an extra chromosome number 21.

2) Single-Gene Abnormalities:

In this type, there is no discrepancy in number of the chromosomes, but one or more genes on the chromosomes are abnormal. Some of these genetic abnormalities are passed on to the child if one of the parents is affected with the same abnormality. This process of genetic transfer is known as autosomal dominant inheritance.

However, some other genetic problems are passed on to the child only if both the parents carry the same defective gene. This mode of inheritance is found in diseases like cystic fibrosis, Tay-Sachs disease, and sickle cell anemia. In these cases both parents are normal, but there is possibility of one in four of their children can be expected to be affected. This is known as autosomal recessive inheritance.

3) Sex linked abnormalities:

A third type of genetic abnormality is called sex-linked, and generally is passed on to the male child only. Girls child can carry the abnormal gene which causes these disorders but cannot suffer from the actual disease. Such diseases include hemophilia, color blindness, and the common forms of muscular dystrophy.

Conditions during Pregnancy affecting The Baby:

Certain illnesses during pregnancy, especially in the first trimester or during the first nine weeks, can cause serious congenital abnormalities. These include German measles and diabetes. Consumption of alcohol and certain drugs during pregnancy significantly increase the risk of a baby born with serious abnormalities.

Some medications taken during pregnancy are toxic and can cause permanent damage to the fetus such as thalidomide. Therefore, it is very important to be cautious before taking any medications or supplements during pregnancy.

Combination of Genetic and Environmental Problems

Some congenital abnormalities can occur when there is a genetic tendency for the condition with combined effect of exposure to certain adverse environmental influences on the fetus within the uterus during some stage of the pregnancy. Examples of such conditions are cleft lip, cleft palate and spina bifida.

Unknown Causes

The majority of congenital malformations occur without any discernable cause. This situation is complicated as the parents cannot plan to have more children because of unpredictability about the possibility of anomaly in second child. In such cases, genetic counseling is very important mode of therapy. These services have knowledge and expertise about various genetic abnormalities. They can be able to advice the parents about the proper course of action against such anomalies.