Objective: To elucidate the relationship between nuchal abnormality, karyotype, and prognosis in fetuses with nuchal thickening or cystic hygroma observed between 10-15 weeks' gestation.
Methods: We reviewed all cases of fetal nuchal thickening (4 mm or greater) in 10-15-week fetuses over a 5-year period. Generalized hydrops and the presence of other anomalies were noted prospectively. We retrospectively measured the nuchal area and determined whether septations were present. Data consisted of karyotype, pathologic studies, and clinical follow-up of live-born infants.
Results: Of 100 consecutive fetuses, 29 were excluded because of pregnancy termination without karyotype or pathologic information. Of the remaining 71 fetuses, 63 had karyotyping. Abnormal karyotypes were found in 31 of 37 hydropic fetuses but in only 12 of 26 nonhydropic fetuses (P < .05). Fetuses with Turner syndrome had larger cystic hygromas than those with trisomy 18, trisomy 21, or normal karyotype (P < .05). There were ten normal live-born infants, none of whom was hydropic at the time of initial diagnosis and all of whom demonstrated spontaneous resolution of the nuchal thickening on subsequent sonograms.
Conclusions: Fetuses with nuchal thickening or cystic hygromas demonstrated by ultrasound should have their karyotype determined. If the karyotype is normal and there are no hydrops or septations, the prognosis is good.