MMP9 and hematoma: ALA supplementation significantly reduces the incidence of spontaneous contractions [32] by decreasing the expression of two enzymes involved in PTB, nuclear factor-kappa B (NF-KB) [34] and metalloproteinase-9 (MMP-9) [35]; moreover, in association with P4, ALA contributes to the faster healing of subchorionic hematomas in patients with threatened miscarriage in comparison to the standard progesterone approach [9].