You have rights whilst pregnant and at work. You have protection from being sacked just because you are pregnant, the right to a reasonable amount of paid time off for antenatal appointments. What is considered 'reasonable' is not defined in law, however, women must try to minimise disruption for their employer's business, but the employer has to have a good reason for not giving permission, and
special health and safety protection. For example, you should be protected from lifting or handling heavy loads, standing or sitting for long periods of time, handling toxic substances, or working long hours.
if you feel you are not being given these rights you should speak to your employer. Or ask your midwife/ doctor to write a letter making it clear that they are affecting yours and the babies health.