The Principles of Clinical Cytogenetics - Extra Materials - Springer

546 Sarah Hutchings Clark
the couple, their ethnicities, and family history, the counselor discusses the potential for increased
risk, if any, and offers any appropriate options for carrier and/or prenatal testing (12). Although in
some cultures consanguinity is accepted and even common, in other cultures it carries a social stigma.
Not only might a consanguineous couple be dealing with an increased risk of abnormalities in their
offspring, but they might also be facing criticism from their family and society. In these situations,
the genetic counselor can provide emotional support and referral to an appropriate support organization.
Advanced Maternal Age
The chance to have a pregnancy or child affected with a chromosome abnormality increases with
advancing maternal age (Table 1) (13). Therefore, the current standard of care is to routinely offer
prenatal diagnosis (see Chapter 12) to all pregnant women who will be 35 or older at their estimated
date of delivery (EDD) (14).
Abnormal Prenatal Screen
Screening can be used, along with maternal age, to estimate the possibility that a fetus is affected
with Down syndrome or trisomy 18. Such aneuploidy screening can be performed through the utilization
of ultrasound, maternal serum, or a combination of the two.
Teratogen Exposure
The term “teratogen” applies to any medication, chemical, or environmental agent that has the
potential to cause adverse effects, such as birth defects, on a developing fetus. When the mother or
father of a current or future pregnancy has been exposed to an agent that could have a detrimental
effect on that pregnancy, a referral to a genetic counselor is appropriate. Of note, certain maternal
conditions, such as phenylketonuria (PKU), which is a metabolic disorder, diabetes, and seizure disorders
increase the risk for birth defects in a pregnancy. The counselor will consult current resources
and discuss with the exposed individual or couple the potential adverse effects associated with the
exposure in question. Any available options for minimizing these potential adverse effects or for
identifying them prenatally are also discussed.
Infertility
Certain chromosome abnormalities and genetic conditions result in varying degrees of infertility
(see Chapter 11). Therefore, when an individual or couple experiences infertility, it is appropriate to
rule out the possible genetic and cytogenetic causes. If such a cause is identified, a genetic counselor
can be important in educating the individual about the condition. The genetic counselor can also
assist the physician in discussing the available options that could allow for reproduction. In addition,
if the individual is able to reproduce using his or her own gametes, the possible recurrence risks for
future offspring should be addressed.
Recurrent Spontaneous Abortion
Miscarriage is more common than many people recognize. In fact, it is estimated that 10 to 15%
of all recognized pregnancies end in miscarriage (15) (see Chapter 13). There are many possible
causes of miscarriage, including a chromosomally abnormal conceptus. Approximately 50% of
recognized first-trimester miscarriages are chromosomally abnormal (10,15,16). In some individuals,
pregnancy loss is recurrent. In addition to having the potential to cause significant psychological
distress, recurrent miscarriage warrants a complete evaluation, which could include genetic,
cytogenetic, and endocrinology studies, in an attempt to identify the cause. As discussed later,
some causes of recurrent miscarriage confer increased reproductive risks for the patient, as well as
his or her family members.