We have studied the layer compression modulus B for smectic liquid crystals near the SmA-SmC*, SmA-SmCA*, SmA-ferrielectric phase transitions. B shows a significant pretransitional softening due to the order parameter fluctuations above the phase transitions, suggesting that these phase transitions are not of the Landau mean-field type. We also measured B near the nematic-SmA and SmA-CryB phase transitions. In the vicinity of the nematic-SmA phase transition, critical exponent of B is in very good agreement with that determined by light scattering. At the SmA-CryB phase transition, B suddenly increases without pretransitional behavior.