If you have a medical condition such as high blood pressure, epilepsy, heart disease, or diabetes, or had certain serious complications in a previous pregnancy, your pregnancy will probably be considered high risk. In this case, you'll need to see an obstetrician, or possibly a perinatologist (a physician who specializes in high-risk pregnancies).
If you're having twins or higher multiples, or if certain problems develop during your pregnancy, you'll need to see an ob-gyn or a perinatologist. In some situations, you may be able to see a midwife and a doctor.