Entry 1 sense Webster, 1913 Postnatal /pōsˌ-tnāt'-əl/ · Post·na·tal · IPA /poʊstˈneɪtəl/ 01 a. After birth; subsequent to birth; as, postnatal infanticide; postnatal diseases. 1. After birth; subsequent to birth; as, postnatal infanticide; postnatal diseases.