Segregation analysis and genetic counseling when both parents carry balanced chromosomal translocations.

OBJECTIVE

To assess the risk of chromosomally abnormal offspring and discuss counseling approach when both parents carry balanced translocations.

DESIGN

Theoretical segregation analysis is performed and use of empiric data is used in genetic counseling.

SETTING

Patients are referred to Division of Reproductive Genetics at the University of Tennessee, Memphis.

PATIENTS, PARTICIPANTS: The mother, heterozygous for reciprocal translocation 46,XX, rcp(7;13)(p21;q22) and father, heterozygous for Robertsonian translocation 45,XY,rob(13q;14q) were referred for genetic counseling concerning risks of chromosomally abnormal offspring.

INTERVENTIONS

Segregation analysis, genetic counseling, and chorionic villus sampling.

MAIN OUTCOME MEASURE(S): A cumulative risk was derived to use for counseling purposes. Cytogenetics using GTG-banding was performed on cultured chorionic villus cells.

RESULTS

Theoretical risk of this couple having chromosomally abnormal offspring was 40.5%. On the basis of empirical data and risk factors inherent in the specific translocations, the maternal contribution at midtrimester was 3.5%; the paternal contribution was 1% to 2%. The sum of these risks was used in counseling.

CONCLUSIONS

The fetus was found to be 46,XY,rcp(7;13)(p21;q22).