Pre-Conception Genetics Testing

By Sandra Glahn

Robin’s brother has hemophilia. She and Kelvin want children, but they wonder, “What are our odds of having a baby with the same problem?”

Bill and Liz have lost four pregnancies. Before Liz conceives again, they want to know if chromosomal abnormalities could be causing their losses and whether to keep trying.

Ben and Sarah’s first child has Tay-Sachs. They are thinking about having another child, but they want to know how much of a gamble they would be taking.

Between two and three percent of children have some major abnormality caused by one of the nearly four thousand disorders linked to genetic causes. Half of these are apparent by birth; the rest will show up later. While good health and fitness do little if anything to prevent hereditary diseases, pre-pregnancy genetic counseling can help couples determine the probability of passing on some of these problems.

Although most couples don’t need it, experts estimate that nearly 15 million Americans could benefit from screening. Those at risk meet one or more of the following criteria:

The husband, wife or one of their relatives has a genetic disorder.
They have a history of three or more miscarriages.
They have experienced stillbirth.
They both belong to an “at risk” ethnic group.

“Genetic counseling” brings to mind an avalanche of vocabulary words from the molecular biologist’s lab. Yet words like odds, risk, gamble and chance are also common terms in the process of testing genes and chromosomes.

Chromosomes are microscopic structures located inside cells. An individual chromosome carries hundreds of thousands of genes, the basic units of heredity that determine everything about a person from eye color to blood type. Each parent contributes randomly to half of the child’s total make-up, except sex determination, which always comes from the father. Abnormalities in the number or structure of chromosomes, or negative factors in the genes they carry, can lead to problems.

Medical personnel with special training in genetics offer consultation. They start by taking detailed family health histories. They then chart a family tree which includes the couple, their immediate family, nieces, nephews, aunts, uncles, first cousins, and grandparents.

In the case of recurrent miscarriage, stillbirth, and a small number of other problems, blood is drawn from both partners and checked for chromosomal abnormalities. When a testable genetic disorder like sickle cell anemia is suspected, blood is sent to a laboratory which specializes in investigating that particular disease.

Based on results of their investigations, experts calculate risk. Walter Taylor, MD, a genetics specialist, says, “`Genetic counselor’ can be a misleading title; our job is not to give advice. We let couples make their own decisions after we provide them with clear, accurate information about the likelihood of something happening. Yet it’s important for couples to realize that even though we check everything, problems can still occur.”

Many problems occur randomly at conception, as with most cases of Down syndrome. Age is also a factor. For this reason, couples who conceive earlier in their childbearing years have better odds of having healthy babies than older couples. Environment may play a small part, too. “We recommend refraining from smoking, drinking and illicit drugs,” says Gail Brookshire, a genetics counselor at Children’s Medical Center, “but it’s doubtful that these actually have an impact before conception. It’s good to be cautious, but we don’t want to create guilt if something goes wrong.”

Most insurance policies cover consultation and lab costs, and results take between one and six weeks, depending on the test. Then, if a couple finds the odds stacked against them, they can decide to try anyway, live without children, adopt, or conceive with donor eggs and/or sperm.

Sometimes, despite favorable odds, something goes wrong. Joe McIlhaney, Jr., MD, author of Dear God, Why Can’t We Have A Baby, says, “I would hate to see the day when we judge everyone by some arbitrary degree of ‘normality.’ Just because children are born with limitations does not mean that they are ‘nonpersons’ or worthless. These children do have limitations, but then so do you and I.”

This article first appeared in Dallas Child.