Is Progesteron useful for fertility?

The provided context does not contain specific information on progesterone for fertility. Generally, progesterone is crucial for regulating the menstrual cycle and supporting early pregnancy, especially for implantation and maintenance. However, its use for fertility requires a diagnosed deficiency or imbalance. Without direct evidence from the given sources, the evidence level is unclear. Caveat: Progesterone is not a universal fertility treatment; hormone therapy should only be used under medical supervision after proper testing.