GSTM1 and Pallister-Hall syndrome: For example, Castoldi et al., 1994 [15] showed that PHs ≥ 2 cm were always symptomatic, and those ≥ 3 cm often caused severe complications, while Ishikawa 2009 [43] demonstrated that a width ≥ 2 cm on immediate ultrasound was the strongest predictor of Hb decline ≥ 10%.