INCREASED NUCHAL TRANSLUCENCY THICKNESS AT 10-14 WEEKS OF GESTATION AS A PREDICTOR OF SEVERE TWIN-TO-TWIN TRANSFUSION SYNDROME

This study examines a possible association between increased nuchal tr anslucency thickness at 10-14 weeks of gestation in monochorionic twin pregnancies and the subsequent development of severe twin-to-twin tra nsfusion syndrome (TTS). In 132 monochorionic twin pregnancies, includ ing 16 that developed severe TTS at 15-22 weeks of gestation and 116 t hat did not develop TTS, crown-rump length, nuchal translucency thickn ess and fetal heart rate were measured at 10-14 weeks. In those that d eveloped severe TTS, the prevalence of nuchal translucency thickness a bove the 95th centile of the normal range and the inter-twin differenc e in nuchal translucency thickness and fetal heart rate were significa ntly higher than in the non-TTS group; there were no significant diffe rences between the groups in the inter-twin difference in crown-rump l ength. For fetal nuchal translucency above the 95th centile, the posit ive and negative predictive values for the development of TTS were 38% and 91%, respectively; the likelihood ratios of nuchal translucency a bove or below the 95th centile for the development of severe TTS were 4.4 (1.8-9.7) and 0.7 (0.4-0.9), respectively. These findings demonstr ate that the underlying hemodynamic changes associated with TTS may ma nifest as increased fetal nuchal translucency thickness at 10-14 weeks of gestation.