Association between increased yolk sac diameter and abnormal karyotypes.

AIMS: To investigate the association between increased yolk sac diameter and abnormal karyotype. METHODS: Retrospective analysis of 42 patients with no history of diabetes between 6 and 12 weeks of gestation with increased yolk sac diameter measuring ≥6 mm was evaluated by transvaginal ultrasound. Sonographic findings were correlated with karyotype. The Fisher's exact test and exact conditional logistic regression analysis were used for statistical analysis. RESULTS: Chromosome abnormalities were found in 76.2% of chorionic villi samples. A statistically significant relationship between karyotype and missed abortion was detected (P=0.001). None of the patients with a yolk size diameter ≥8 mm and viable pregnancy had a normal karyotype. Trisomy 15 or 16 was strongly associated with missed abortion (unadjusted odds ratio=14.97, P=0.01). Nine patients with viable pregnancy had a yolk sac ≥6 mm (six patients with normal karyotype, one patient with monosomy X, one patient with trisomy 16, and one patient with trisomy 21). CONCLUSION: Our data indicate that enlarged yolk sac may also be visualized in viable pregnancies. Patients with an enlarged yolk sac and normal karyotype require detailed ultrasound evaluation in the second and third trimester.