WordNet records no synonym and no antonym for perinatology. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the branch of obstetrics concerned with the anatomy and physiology and diagnosis and treatment of disorders of the mother and the fetus or newborn baby during late pregnancy and childbirth and the puerperium
Synonyms, antonyms and the broader and narrower relations for perinatology come from Princeton University’s WordNet. Full sources and licences.