No, she does probably not have any rights to attend a birthing class during work hours (though if she has vacation or comp time, she should be entitled to use it):1) The Family and Medical Leave Act and the similar laws that many states have provide unpaid time off for medical care or the birth (or post-birth care) of a child; but attending a birthing class is not itself birth, and it is not necessary medical care (i.e. care for an injury or illness).2) An employer may not discriminate agaist women for being pregnant--but it is not discrimination to not let your wife take time off this class *unless* it is the case that the employer has let employers take time off for non-pregnancy, non-work related classes in the past (e.g. for personal training; for a writing workshop; etc.). If people could take time off for non-pregnancy related classes, then barring your wife from the birthing class could be discrimination.