by Wendy Bulawa

Created on: July 15, 2008   Last Updated: July 18, 2008

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 couplesnone 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

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