X + Y = ?? : Genetics and Your Baby

I’m not a mathematician, nor do I aspire to be one. In fact, I’ve probably flunked a math quiz or two during my illustrious career as a student. Yet, soon-to-be parents or couples considering procreation may want to brush up on basic math and biology given that the number of chromosomes your future child has plays an enormous role in their genetic makeup.

When a human egg is fertilized, it takes on the composition of 23 pairs of chromosomes from a mother and 23 pairs from a father-- resulting in a total of 46 pairs. That is, of course, unless Mother Nature waves her magic wand and adds or subtracts pairs or pieces-parts, thus creating a monosomy (missing a chromosome from a pair) or a trisomy (more than two chromosomes in a pair). An example of a condition caused by a trisomy is Down syndrome (individual is born with three copies of chromosome 21 rather than two) while Turner Syndrome would exemplify a monosomy (an individual is born with only one sex chromosome, an X). 

A recent article in the American College of Obstetricians and Gynecologists (ACOG) Practice Bulletin (January 2007; Number 77) titled “Screening for Fetal Chromosomal Abnormalities” recommended that all pregnant women (not just those 35 years and older) be offered genetic screening of their unborn fetus. This recommendation generates a series of complicated issues for expectant couples—none of which I’m qualified to address.

What is important to consider given the recommendation is an option many may not be familiar with called: genetic counseling. Before undertaking any form of genetic screening or testing, women and couples can take advantage of genetic counseling, defined as a an educational process helping individuals, couples or families understand how genetic makeup and family history play a role in reproduction.

Those who benefit from genetic counseling include individuals with a family history of genetic abnormalities, those belonging to a specific ethnic group in which a higher incidence of certain genetic disorders exists, or those who have positive results on routinely-offered screening (i.e. amniocentesis).

Once engaged, genetic counselors can outline recurrence risks, discuss screening procedures and provide genetic testing for individuals or couples seeking more information prior to undertaking natural or assisted reproduction (in vitro fertilization).

The National Birth Defects Center (NBDC) of Waltham, Mass, supported by The Genesis Fund, offers such counseling in addition to a list of support services for individuals with genetic conditions. 

Dr. Catherine Bearce Nowak, Associate Physician-in-Chief and Director of Clinical Services at NBDC, believes that genetic counseling is best done pre-conception to allow couples to obtain knowledge about their chance of having a child with a genetic condition and put those results and risks into context. The NBDC also offers genetic counseling for women who have concerns about exposure to medication, drugs or chemicals during pregnancy.

“Many people have never thought about their individual or family's genetic health. Others aren’t aware of various screening tests and therefore haven't given thought about whether or not they are interested in pursuing them. A genetic counselor can review family history and explain the pros and cons of the tests so that couples feel empowered to make whatever choice fits best for them and not feel pressured to do testing they’d otherwise prefer not do.”  

According to Dr. Nowak, most diseases such as heart disease and cancer are the result of both lifestyle factors and genetic predisposition. “Knowing about diseases that run in your family allows you to make lifestyle changes which can protect you and your children.  Through genetic counseling, individuals may also discover purely hereditary conditions which may also have an impact.” Many families only discover a genetic condition in the bloodline after asking a lot of questions about family history.

Genetics and Infertility

For couples struggling to conceive naturally or those undergoing fertility treatments, genetic counseling may be worthwhile. Dr. Nowak said, “Sometimes a chromosomal rearrangement in one person in the couple can cause infertility due to increased rate of chromosomal abnormalities in the eggs or sperm, although that abnormality doesn't cause that person any health consequence.  When such a situation is identified, couples can be counseled about which assisted reproductive procedures will have the best chance for success.” 

To identify the genetic makeup of an individual, a blood test is often performed to capture one’s DNA structure. Some individuals opt to undergo such genetic testing to determine the risks of inherited hereditary conditions while others complete testing to determine risks of chromosomal abnormalities in a fetus—and several other reasons in between.

Today, embryos cultivated through in vitro fertilization (IVF) can even be genetically tested at an early state of development to determine if a chromosomal abnormality exists. This advance in medical and reproductive science called Pre-implantation Genetic Diagnosis (PGD) allows couples with known hereditary conditions to screen for them prior to implantation.

The cost associated with genetic counseling and genetic testing which spans blood work through PGD analysis can reach into the thousands of dollar range. However, couples should discuss their interest in genetic counseling and related screening procedures with their insurance carrier first to find out if any are covered under current policies. 



By Wendy Bulawa
GateHouse News Service
March 27, 2006