A couple is planning to have their first child and request to speak with a genetic counselor. The woman explains that she had a sister who died in childhood with Down syndrome. There is no other family history of the condition. What is the most appropriate counseling for them?

Down syndrome is generally infrequent, so there is no increased risk to this couple.

If her sister's karyotype analysis cannot be done, the woman herself should have chromosomal analysis.

The pregnancy of the woman will be screened in the second trimester using alphafetoprotein, bhCG, and unconjugated estriol, which will be sufficient to detect Down syndrome, if it has occurred.

The couple should obtain prenatal diagnosis by chorionic villus sampling or amniocentesis.