CROWN-RUMP LENGTH IN CHROMOSOMALLY ABNORMAL FETUSES AT 10 TO 13 WEEKSGESTATION

OBJECTIVE: Our purpose was to investigate whether fetuses with aneuplo idies demonstrate evidence of growth retardation during the first trim ester. STUDY DESIGN: This was a retrospective, cross-sectional study o f singleton pregnancies undergoing fetal karyotyping at 10 to 13 weeks ' gestation. Measurements of crown-rump length in 135 chromosomally ab normal fetuses were compared with those in 700 chromosomally normal fe tuses. RESULTS: The median crown-rump length of fetuses with trisomy 1 8 (n = 32) was significantly reduced. In contrast, in fetuses with tri somy 21 (n = 72), trisomy 13 (n = 11), 47,XXX (n = 6), 47,XXY (n = 6), 45,X (n = 5), and triploidy (n = 3) the crown-rump length was not low er than normal. CONCLUSION: At 10 to 13 weeks' gestation fetuses with trisomy 18 are growth retarded, whereas in trisomy 21, trisomy 13, and sex chromosome aneuploidy growth is normal.