the Equal Pay Act and Sex Discrimination Act in the 70s have made it more worthwhile for women to get jobs as they can earn a good wage in a fulfilling job
younger women are now building a career and will likely not have children until they are older and have a established career, reducing the amount of time they can have children before they are biologically incapable.
several women may choose not to have children at all due to not wanting to disrupt their successful career and rejecting a traditional housewife role