You should see only one obstetrician so you can avoid always having to discuss your medical history, or do tests, or have to take the time to know the doctor. My obstetrician for both pregnancies was Dr Jen Shek Wei (also gynae). Since we already knew each other, each appointment is quicker and...
I would also like to recommend Dr Jen Shek Wei from the Women's Clinic of Singapore. His clinic is just at Ang Mo Kio Ave. He's my gynae and he's really quite skilled and friendly. Appointments are not at all awkward.