Is it valid to vow to fast every Monday and Thursday if the newborn is male, with the exception of days of fatigue and the husband's objection? And does one have to make up for the days of menstruation and postpartum bleeding that were not explicitly excepted? And must the vow be fulfilled as soon as the gender of the fetus is known or after birth?

A low-form oath of covenant is a valid vow. The exception for days of fatigue or lack of the husband's permission is valid if it is connected to the speech and intended before finishing (the vow). As for days of menstruation, they are legally exempted, and there is no make-up or expiation for what she missed due to any of these reasons. Fulfilling the vow does not begin merely by informing the doctor, but rather after childbirth and ensuring the safety of the newborn. If the questioner is unable to fulfill her vow, she must offer an expiation for an oath.