No, the validity of a contract cannot be made subject to such conditions.
The club will be deemed to have terminated the contract without just cause.
It shall be presumed, unless proven to the contrary, that the unilateral termination of a contract by a club during a pregnancy or maternity leave occurred as a result of a player being or becoming pregnant.
Sporting sanctions in addition to the obligation to pay compensation
The club shall be banned from registering any new female players, either nationally or internationally, for two entire and consecutive registration periods.
To return to football activity after the completion of their maternity leave
To continue providing sporting services to their club (i.e. playing and training), following confirmation from their treating practitioner and an independent medical professional (chosen by agreement between the players and their clubs) that it is safe for them to do so
Yes, associations can set different registration periods for male and female players.