Gynaecology is a specialist of medicine, in order to get there you need to do a medicine degree then a further 7 years of speciality training. That’s 12 years total at a minimum. There are other ways into medicine other than a levels but a levels would probably be the most straight forward route if you can get the GCSEs for it.
Other routes in gynaecology include gynaecology nursing but you would not be a ‘gynaecologist’ as that’s a consultant level position in medicine.