OBJECTIVE: The objective of this study was to assess the clinical use of routinely karyotyping spontaneous abortion material.

STUDY DESIGN: We retrospectively reviewed the records of the Pittsburgh Cytogenetics Laboratory from January 1, 1998, to December 31, 2001, for all tissues from spontaneous losses at 20 weeks' gestation or less for which complete medical records were available.

RESULTS: There were 517 submitted samples of which 28 (5.4%) failed to grow in culture. Overall, 55.8% of samples were abnormal; 52.3% of normal results were male. In samples from pregnancies at 13 weeks or less the rate of abnormality was 69.1%. When analyzed by maternal age, the rate of abnormality for first-trimester losses was 57.2% in women younger than 35 years, and 82.3% in those 35 years or older. There was no difference in the rate of abnormality when comparing first loss with two or more losses, first pregnancy with two or more pregnancies, or the presence or absence of at least one live birth.

CONCLUSION: Chromosome abnormalities are the cause for pregnancy loss in 50% to 80% of cases, depending on maternal age and gestational age at time of the loss. Karyotyping of spontaneous losses in the first trimester beginning with the patient's second loss provides clinically important etiologic information and decreases the number of evaluations necessary for recurrent pregnancy loss.