A perinatologist is a physician who does high risk obstetrics. They train as an obstetrician and then do extra training in high risk care of both mother and fetus. Half of pregnancies in the United States are now high risk because the mother is older, younger, hypertensive, diabetic, had heart surgery, hip surgery, has a serious infection, had gynecological surgery, develops preeclampsia, preterm labor, twins, triplets, quintuplets, etc. Most high risk pregnancies are still cared for by an obstetrician, family practice physician or midwife, often in consultation with the perinatologist.