My son in engaged to a beautiful girl whose father has a cleft lip that is quite noticeable. What are the chances of their child being born with this abnormality, and what can be done to correct it? As far as I know, there is no abnormality such as this in my son's heredity.

Elizabeth

Estimating the probability that your grandchild will be born with a cleft lip is difficult, but I can give you a rough idea of the odds. Analysis of this problem depends a great deal on knowing some details of the affected grandfather's medical history. Specifically, was his cleft lip associated with other abnormalities, and, if so, was a specific syndrome ever identified?

First, let's assume that the grandfather's cleft lip was an isolated abnormality, and let's assume that your future daughter-in-law was not born with a cleft lip. (In other words, she was not born with a mild cleft lip, the repair of which has escaped your detection.) In this situation, the chance that your grandchild will be born with a cleft lip is probably very close to the risk for the general population (1 in 1,000).

What if the grandfather was born with a genetic syndrome? Then the risk estimate depends greatly on knowing the mode of inheritance of the syndrome. For example, some syndromes have autosomal dominant inheritance with incomplete penetrance. Translation: If a man has such a syndrome, there is a 50 percent chance that any one of his children will be born with the same syndrome (autosomal dominant inheritance), but not all afflicted children will have the same degree of problems as the father (incomplete penetrance). In this example, a child might have the gene for the syndrome and yet not have any outward manifestations of the syndrome. This child could grow up and have children, and there would be a 50 percent chance that any one of his or her children could inherit the gene. These children may not be so lucky -- unlike their parent, they may have a more severe form of the syndrome. Incomplete penetrance thus introduces a great deal of uncertainty into the discussion.

Let's take another example: What if the grandfather has a syndrome with autosomal recessive inheritance? In this case, all of his children (including your future daughter-in-law) will be carriers of the syndrome, but each one will be outwardly normal. Only if his daughter is unlucky enough to marry another carrier will there be any chance (25 percent, to be exact) that one of their children will have the same syndrome.

The foregoing discussion will make sense to you only if you remember Mendelian genetics from high school biology. For a quick primer on this topic, a good starting place is the Genetic Learning Science Center.

A specialist called a medical geneticist) is trained to take careful family histories, examine family members for subtle signs of malformations and draw appropriate conclusions. A medical geneticist would meet with your son and future daughter-in-law and would probably also want to meet with her father and as many of her siblings as possible. Afterwards, this specialist could give you an educated rough estimate of risk. If you are interested in finding a medical geneticist in your area, you should contact the American College of Medical Genetics.

You have also asked about correction of cleft lip. Cleft lip is very correctable, but such surgery is best left to specialists who perform this operation on a regular basis. The best care is usually provided by a craniofacial team (consisting of pediatric plastic surgeons, otolaryngologists, speech therapists, dentists, medical geneticists and many others). Most medical centers and large pediatric hospitals have such a team. If you would like some idea of what constitutes a craniofacial team, take a look at this site describing the craniofacial team for the Medical College of Georgia. This site also provides information on surgery for cleft lip and cleft palate.