WEEKLY NUCHAL TRANSLUCENCY MEASUREMENTS IN NORMAL FETUSES

Objective: To examine the longitudinal course of nuchal translucency t hickness by weekly measurements between 10 and 15 weeks' gestation in normal fetuses. Methods: Nuchal translucency was measured weekly from 10 to 15 weeks' gestation in 64 fetuses with normal pregnancy outcome. The median and the fifth, 25th, 75th, and 95th percentiles were calcu lated. Results: Nuchal translucency measurements varied considerably w ith gestational age; this variation followed a fetus-specific pattern. In 94% of cases, we observed an increase followed by a steady decreas e in nuchal translucency measurement. A visible nuchal translucency wa s found after 76 and 86 days' gestation in 97% (95% confidence interva l [CI] 89, 100) and 100% (95% CI 94, 100) of the fetuses, respectively . The median nuchal translucency increased from 0.7 mm at 70 days' ges tation to 1.7 mm at 91 days' gestation, after which it declined to 1.0 mm at 105 days' gestation. Conclusion: A progressive increase and sub sequent decrease in nuchal translucency thickness occurs with advancin g gestation in most fetuses, but the timing of the peak thickening app ears to be fetus-specific. In this study, each fetus developed a visib le nuchal translucency. If the nuchal translucency measurement is 0 mm before 12 weeks, it may be advisable to repeat the measurement at 12 weeks' gestation. In contrast, a nuchal translucency that cannot be me asured from 12 weeks' gestation onward suggests that this temporary an atomic entity is already in its waning phase. (C) 1998 by The American College of Obstetricians and Gynecologists.