@HesDeadBenYouCanStopNow that is a very fair point. As with a lot of things in life there are good and poor employers, managers and employees. Who holds the power in the relationship is a factor. No one knows the OP, her employer nor her manager.
If for example the OP works Sunday-Wed and Friday, as she is struggling with her pregnancy her manager may have said as you are struggling would it be better to swap your NWD so you work Sun-Tue and Thur -Fri and break the week up more evenly (3 days NWD 2days). This would also mean you don’t have to do so much travelling to get to and from your antenatal appointment and work.
Alternatively they might have said I’m fed up of you having your antenatal appointments on a Thurs, you either need to arrange them for your NWD or as I’ve agreed several times to swap your NWD so you can do xyz Im going to ask you to swap your NWD or I will be less flexible in the future.
Very different scenarios, one thinking how to help the OP one not.
Calling some posters horrible, appalling, discriminatory or unlawful for saying it’s not unreasonable to ask the question have immediately assumed it is the latter scenario not the first.
The Employment Rights Act states (2)An employee is not entitled to take time off under this section to keep an appointment unless, if her employer requests her to do so, she produces for his inspection—
(a)a certificate from a registered medical practitioner, registered midwife or [F1registered nurse] stating that the employee is pregnant, and
(b)an appointment card or some other document showing that the appointment has been made.
Legally as a manager I could refuse to allow the time off if these documents are not produced. I think a lot of posters would consider me unreasonable even though it’s lawful. IRL I have never asked for, nor been shown either of these documents, I have trusted my staff.