Yes, as long as you have at least 12 weeks' service in the same role with the same hirer, but the time off will be unpaid. You are entitled to unpaid time off to accompany your partner to up to two antenatal appointments. The time off is capped at six and a half hours per appointment.
The employer is not allowed to ask for evidence of the appointment because the appointment card belongs to your partner. However, the employer can ask for a signed declaration stating the date and time of the appointment and confirming you are in a qualifying relationship with your partner or her expected child, and that the purpose of the time off is to accompany her to the appointment, made on the advice of a GP or midwife.