Women in Motion

Susan Blatt, MD

Everyone has a different genetic make-up.  When children are conceived, they receive a mixture of genes from both parents, allowing traits such as hair color to be passed on to future generations.  In the past few years, after successful completion of the Human Genome Project, much more is known about genetics and its relationship to medical problems.

Before a woman becomes pregnant, she should consider whether or not genetic diseases have occurred in her family or in her partner’s family.  If so, the couple should consult an obstetrician, pediatrician, or genetic counselor.  Regarding some diseases, such as sickle cell anemia, adults can be tested to see if they are carriers.  This may help a couple understand their risk of having a child with a problem. Tests can be done during a pregnancy, to determine whether or not the fetus has the disease.  A blood test called the “triple test”, chorionic villus sampling (CVS), and amniocentesis are the usual tests used. These tests are optional and are usually only done if a woman would consider terminating a pregnancy.

Children born with Down’s syndrome have an extra chromosome in each cell of their body.  This results in a pattern of abnormalities such as specific facial features, abnormal voice quality, and mental retardation.  Down’s syndrome occurs more commonly in older women who become pregnant.  Blood tests done early in a pregnancy may indicate the possibility of Down’s syndrome.  CVS and amniocentesis are used to visualize the cells of the fetus and establish the diagnosis during pregnancy.

Whereas Down’s syndrome is caused by an extra chromosome, some diseases are caused by a single abnormal gene.  Cystic fibrosis is the most common of these disorders. This is a chronic lung disease of childhood that is usually fatal by the age of thirty. In this disease, an abnormal gene comes from each parent; a fetus with two abnormal genes develops the disease.  In the last few years this abnormal gene has been identified and can be specifically tested for during pregnancy. 

Spina bifida and anencephaly are two anatomic defects that tend to run in families, but there is not an abnormal gene.  The triple test is combined with a sonogram to diagnose these problems.  Anencephaly is absence of the skull and brain.  It is usually fatal within a few days after birth.  Spina bifida is a defect of the lower spine.  These children are physically handicapped, but mental development is often normal.  Both of these defects are less likely in women who have adequate intake of folic acid.

Around the year 2000 the human genome was mapped.  Since then it has been possible to determine a specific abnormal gene and whether or not it is present in a fetus.  This is a major step forward in making sure that children are born healthy and that they have the potential for normal development.