Reduce risk for fetal anomalies before the pregnancy
Recommendations for investigation and treatment prior to pregnancy for reducing
risks of defects or genetic diseases
- Determination of the mother's immune status for a number of viruses or bacteria
that may cause defects if she is infected with them during pregnancy.
- Performing a test for carrier status of diseases such as Tay Sachs disease, Thallassemia in groups who tend to have a high frequency
of the disease.
- Performing tests using modern molecular methods for carrier status of other common
severe genetic syndromes that are preventable (cystic
fibrosis for example).
- Taking prophylactic folic acid medication in order to reduce the risk for congenital
defects in general, and for central nervous system and heart defects and cleft lip and palate in particular.
It is important to perform a number of blood tests to check whether the mother has
immunity to those viruses and bacteria that are associated with causing fetal defects
if she becomes infected during pregnancy. The pathogens in question, which are known
by the acronym TORCHS,
are Toxoplasma, Rubella (German measles), Cytomegalovirus, Herpes virus, and Syphilis.
This is a blood test that is performed routinely during pregnancy, but doing it
before pregnancy is advantageous.
- If you are not immune to rubella, then even if you have been vaccinated in the past
it is advisable to be vaccinated before pregnancy.
- If tests show that you are not immune to toxoplasma, it is advisable to avoid contact
with animals, especially dogs and cats. The information derived from these tests
may also help to interpret with greater accuracy the results of blood tests performed
during pregnancy in order to establish whether or not an infection has occurred
- Regarding cytomegalovirus and herpes virus, if you are not immune, it is important
for you to monitor changes in antibody levels during your pregnancy. Here too, results
of tests carried out before pregnancy are often important for the accurate interpretation
of the results of blood tests performed during pregnancy in order to establish whether
or not an infection has occurred during pregnancy.
Tay Sachs disease
This is a degenerative hereditary disease that is relatively common in Israel. It
manifests as progressive brain degeneration that starts at the age of approximately
8 months in infants who develop normally up to that age.
The degeneration eventually leads to death at about the age of two.
Couples who are both carriers of the defective gene have a 25% risk in each pregnancy
of having an affected child (see autosomal recessive inheritance).
This gene is common in Jews, especially those of Ashkenazi or North African origin.
However, it has also been reported in Jews from other ethnic groups.Carrier testing
is therefore advisable for all couples considering pregnancy or when the woman is
already pregnant, irrespective of ethnic origin.
The test has been carried out in Israel through the Ministry of Health for decades,
and the number of patients in Israel has decreased significantly to almost zero.
To test for Tay Sachs disease, a blood test is carried out in which the level of
the enzyme responsible for the disease is determined; in carriers, the level is
decreased. The test is less reliable in pregnant women, so in these cases, or when
a woman is taking birth control pills, it is best to refer her partner for testing.
If the woman is not pregnant, she can undergo testing herself. In cases where one
partner has been found to be a carrier, the other partner is asked to come for testing,
and if both are found to be carriers they are invited to come for genetic counseling, during which it will be recommended
that the mother undergo prenatal diagnosis in order to examine the fetus. Exact
fetal diagnosis can be performed using
chorionic villi or amniotic fluid cells. It is advisable to perform carrier
testing before pregnancy, but it can also be done in the first weeks of gestation.
Molecular carrier screening
Today, carrier status can be diagnosed for a number of genetic syndromes that are
common in various ethnic groups. Since different diseases are common in different
ethnic groups, it is important to consult your physician or genetic counselor and
read the information about the various diseases in order to know what tests you
should have done. Before deciding, it is important to ascertain the ethnic origins
of both parents of each partner (including the birthplace of grandparents) in order
to be able to recommend which tests should be performed.
When should testing be performed?
The tests should ideally be performed before pregnancy, but can also be done in
the first weeks of gestation.
Preventive therapy: folic acid
Studies over the past 20 years have found that folic acid can help to reduce the
open defects of the central nervous system. Subsequently it has also been
found that this vitamin reduces the risk for cleft lip and palate and heart disorders.
In studies of large populations of healthy subjects, it was found that administering
folic acid with multivitamins significantly reduces the total risk for structural
defects by about 35% or more. Therefore if the mother has no family history but
has had a previous pregnancy with a fetus with defects of the types listed above,
she should take multivitamins containing 0.4 mg or 0.8 mg folic acid. Another possibility
is to take tablets containing only folic acid at a dose of 0.4 mg from about three
months before pregnancy and for the first three months of gestation.
In cases where the mother is in a high-risk group for having a child with a defect
of this kind, a small dose of multivitamins is insufficient. In these cases the
recommended dosage is 4.5 mg folic acid a day for at least eight weeks before becoming
pregnant through to the end of the first trimester of gestation. From the fourth
month of pregnancy it is advisable for all women to take a combined iron (100 mg)
and folic acid (0.5 mg) preparation.
Folic acid prevents these defects in 70% of cases; however it does not constitute
an alternative to appropriate monitoring, genetic counseling, ultrasonic follow-up,
alpha-fetoprotein testing within biochemical marker testing, or amniocentesis. These tests provide for diagnoses
of defects in the fetus.