As a general rule, genetic counseling should be sought by prospective parents if:

* There is a family history of genetic disorder.

* They have a child with a genetic disorder.

* The mother is 35 or older.

* The mother has had three or more miscarriages

* Both parents are Jewish (for Tay-Sachs disease).

* Both parents are black (for sickle-cell anemia).

* The parents are of English or Irish extraction (for neural tube defects).

* There has been exposure to X-ray or other radiation, or to an increasing number of drugs (even caffeine in large doses) and infections (like rubella) suspected or known to cause birth defects.

In an increasing number of cases, persons at risk for bearing children with genetic abnormalities can be detected even before pregnancy.

After pregnancy has occurred, prenatal diagnoses can be made by combinations of blood tests, sonography (ultrasound techniques) and through amniocentesis. Counseling should begin by the 14th week of the pregnancy. Amniocentesis is usually done 17 weeks after the last menstrual period, up to 20 to 23 1/2 weeks, depending on the tests.

The genetic counselor does not advise the parents on what to do, only on their options.

Among centers where counseling is available: Columbia Hospital, Genetic Consultants, Georgetown University, George Washington University, Howard University, Johns Hopkins University, Baltimore.