A subspecialty of obstetrics concerned with the care of the fetus and sophisticated, high-risk pregnancies. Perinatology is also known as maternal-fetal medicine. In addition to four years of residency training in obstetrics and gynecology the maternal-fetal medicine subspecialist has received two to 3 years of education within the diagnosis and treatment of disorders of the mother and fetus. The maternal-fetal medicine specialist typically works in consultation with the obstetrician. Some of the services provided by the maternal-fetal specialist include diabetes care, management of multiple gestations, level II ultrasound of the fetus, villus sampling, genetic amniocentesis, and in some centers fetal surgery or treatment.