An obstetrical expert or subspecialist concerned with the care of the mother and fetus at higher-than-normal risk for complications: Because Rose was older than normal for expecting her first baby, she was cared for by a perinatologist in the hospital, who made sure that she received any medical treatment necessary before giving birth to her newborn.

A perinatologist logically could be an obstetrician or pediatrician, but in practice, a perinatologist is an obstetrician.

The comparable area of pediatrics is neonatology. A high-risk baby might be cared for by a perinatologist before birth and by a neonatologist after birth.